Computer Solid State Physics Laboratory

/ Takashi Iizuka / Professor
/ Victor I. Ryzhii / Professor
/ Irina I. Khmyrova / Assistant Professor
/ G. Y. Khrenov / Assistant Professor
/ Maxim Yu. Ershov / Research Associate
/ Maxim V. Ryzhii / Research Associate

The main fields of research activity of the Computer Solid State Physics Laboratory are as follows:

• Computer simulation of electron transport in unstrained and strained silicon, silicon-germanium and silicon-carbon alloys.
• Computer simulation of hot-electron transport in heterojunction bipolar transistors based on compound system.
• Theory and modeling of semiconductor devices incorporating resonant-tunneling structures.
• Theory and modeling of novel quantum photodetectors for infrared radiation.
• Preliminary investigation of diamond thin film growth and characterization for future devices.
• Experimental study of the mechanical properties of semiconductor crystals.

• Semiconductor Science and Technology - 3
• Solid State Electronics - 4
• Japanese Journal of Applied Physics - 5
• Infrared Physics - 1
• Journal of Physics - 1

• 6th International Conference on Modulated Semiconductor Structures (Germany) - 2
• International Workshop on Computational Electronics (Great Britain) - 1
• International Workshop on VLSI Process and Device Modeling (Japan) - 1
• International Conference on VLSI and CAD (Korea) - 1
• International Conference on Advanced Microelectronic Devices and Processing (Japan) - 4
• International Workshop on Numerical Modeling of Processes and Devices for Integrated Circuits (USA) - 2

The laboratory is engaged also in the development of computer programs for computer-aided teaching of physics of semiconductors and semiconductor devices.

Refereed Journal Papers

1. M. Tajima, T. Iizuka, and Y. Okada. Direct observation of growth striations in a liquid encapculated Czochralski Gap crystal by light scattering method. Jpn. J.Appl. Phys. Part 1, 32(6A):2592-2596, 1993.

   Growth striations in a liquid encapusulated Czochralski (LEC) GaP crystal doped with Te at the concentration of were examined by the -angle light scattering method. The growth striations were manifested as a periodic fluctuation in the scattering intensity along the growth direction in the core region of the crystal. The striations were found to be clearly correlated with chemical etching pattern, periodical Te fluctuation detected by electron-probe X-ray microanalysis and a periodical cathodoluminescence signal by Te donor. The origin of the striated scattering pattern is attributed to the periodical distribution of the scattering centers formed by the preferential precipitation of excess Te on grown-in dislocations.

   
   

2. T. Iizuka and Y. Okada. Study of scratch-induced mechanical damage on silicon (111) surfaces. Jpn. J. Appl. Phys. Part 1, 33(3A):1427-1434, 1994.

   Scratch-induced mechanical damage on silicon (111) surfaces, in particular the fractures, residual strain fields and anneal-induced dislocations generated by and direction scratches, is investigated by optical microscopy, X-ray diffraction topography and a copper decoration method. The asymmetry in this damage in the [] and reverse [] direcions is observed. The asymmetries are correlated with each other and are discussed in terms of the inclined [] cleavage plane whose intersection with the (111) surface is perpendicular to the direction.

   
   

3. T. Iizuka and Y. Okada. Asymmetry in indentation-induced mechanical damage on silicon (111) surfaces. Jpn. J. Appl. Phys. Part 1, 33(3A):1435-1442, 1994.

   Asymmetry in indentation-induced mechanical damage on silicon (111) surfaces is investigated by using optical microscopy and X-ray diffraction topography. Cracks, residual strain fields and anneal-induced dislocation rosettes around the indentation are found to represent the asymmetries in the [] and reverse [] directions on the (111) surfaces. The crack formation along three directions and the residual strain field distribution along directions are discussed in terms of dislocation reaction and silicon crystal structure, respectively.

   
   

4. G. Khrenov, V. Ryzhii, and S. Kartashov. Monte Carlo modeling of hot electron relaxation in the base region of AlInAs/GaInAs heterojunction bipolar transistors. Semicond Science and Technology, 9(3):329-332, 1994.

   An ensemble Monte Carlo particle simulation of AlInAs/GaInAs heterojunction bipolar transistors was carried out to investigate the influence of the hot-electron transport regime in the base on the steady-state and high-frequency characteristics of the device. It was found that the electron transport in the base is ballistic or near-ballistic for base thickness W and is diffusive for W .

   
   

5. V. Ryzhii. A bistable resonant-tunneling hot electron infrared phototransistor. Semicond.Science and Technology, 9(1):26-29, 1994.

   A resonant-tunneling hot-electron phototransistor (RTHEPT) utilizing intraband absorption of radiation is reported. The mechanism of operation is the resonant-tunneling process controlled by electron photoemission from the base into the collector. The photoelectric performance of the RTHEPT is evaluated using an analytical model. It is shown that the RTHEPT exhibits optical bistability. RTHEPTs can be used as optoelectronic switching devices and photodetectors for infrared radiation

   
   

6. G. Khrenov, V. Ryzhii, and A. Zhakharova. Negative differential resistance of single barrier interband tunneling diodes. Solid State Electronics, 36(9):1325-1333, 1993.

   Evaluation of the characteristics of single barrier structures made from InAs, GaSband AlGaSb is presented using a two-band model based on kp method. Band-bending is calculated by solving Poisson's equation. The transfer matrix method is used for the calculation of the transmission probability for interband tunneling processes. It was shown that peak current density in the InAs/AlGaSb/GaSb heterostructures can be much greater than in the InAs/AlGaSb/InAs diodes.

   
   

7. L. Fedichkin, V. Ryzhii, and V. V'yurkov. Photovoltaic effect in non-uniform quantum wires. Journal of Physics: Condens.Matter, 5:6091-6097, 1993.

   Photon-induced intersubband scattering in a quantum ballistic channel (QBC) is investigated. Our calculations show that light absorption in a QBC with a non-uniform narrowed end can lead to a photovoltaic effect. Using a mode-matching technique the photocurrent is obtained. The evaluated responsivity, detectivity and band width of the proposed photovoltaic detector are conductive to practical application.

   
   

8. V. Ryzhii. The bistability effect in resonant-tunneling phototransistors with multiple quantum well structure. Semicond.Science and Technology, 9:1209-1214, 1994.

   A bistable operation of resonant-tunneling phototransistors incorporating a multiple-quantum well base (RTQWPT) is reported. The operation mechanism is the resonant-tunneling (RT) hot-electron injection controlled by the electron photoemission from the multiple-quantum well (QW) base into the collector. The RTQWPT utilizes intersubband optical absorption in the infrared region of spectrum. The RTQWPT can be used as high efficiency optoelectronic switch controlled by infrared radiation and infrared photodetector.

   
   

9. V. Ryzhii. Infrared hot-electron phototransistor. Jpn Journal of Appl. Physics, 33(1):78-82, 1994.

   A hot-electron phototransistor (HEPT) is proposed and discussed. The HEPT utilizes the intraband absorption of radiation in the base. The two-terminal device can operate as a photodetector for the infrared region of the spectrum. Photoelectric performances of the HEPT are evaluated using an analytical model.

   
   

10. G. Khrenov, V. Ryzhii, and S. Kartashov. AlGaAs/GaAs HBT collector optimization for high-frequency performance. Solid-State Electronics, 37(1):213-214, 1994.

    The investigation of the dependence of the optimum collector space-charge region thickness as a function of the collector series resistance value (collector series resistance is usually greater than emitter series resistance) is carried out.

    
    

11. V. Pankratov and V. Ryzhii. Monte Carlo simulation of gate leakage current effect in p-channel GaAs/AlGaAs HIGFET. Solid-State Electronics, 37(1):211-212, 1994.

    The ensemble Monte Carlo particle method is used to find spatial distributions of the gate leakage current in p-channel HIGFETs and their performance is evaluated.

    
    

12. M. Ershov and V. Ryzhii. High-field electron transport in SiGe alloy. Jpn Journ. of Appl. Physics, 33, Part 1(3A):1365-1371, 1994.

    Electron transport in unstrained SiGe alloy is studied using the Monte Carlo simulation technique. Electron transport characteristics (drift velocity, impact ionization coefficient (II), etc.) are evaluated over a wide range of electric fields. It is found that not only low-field mobility but also saturation velocity and impact ionization coefficients are reduced with increasing Ge fraction due to alloy scattering. More importantly, the high-energy electron population is reduced to a much greater extent than the ionization coefficient. Simple analytical expressions for electron low-field mobility, saturation velocity and II coefficient which can be easily implemented in device simulation programs are proposed.

    
    

13. V. Ryzhii and I. Khmyrova. Bistability effect in laser-transistor resonant-tunneling structure. Solid-State Electronics, 37(4-6):1259-1262, 1994.

    The analysis of the operation of a laser-bipolar transistor incorporating a resonant-tunneling structure (RTLBT) is presented. An analytical model of RTLBT is proposed and used. It is shown that RTLBT can exhibit a bistable operation in a certain range of collector voltage, where the collector and base currents, and the stimulated photon emission intensity are associated with a mobile electron space charge in the collector that influences the electron transparency of the resonant-tunneling structure and the pumping conditions of the laser active region.

    
    

14. L. Fedichkin, V. Ryzhii, and V. V`yurkov. Novel tunable infrared detector based on quantum channels. Infrared Physics, 34(5):477-480, 1993.

    We consider the possibility of infrared signal detection using photon-induced intersubband scattering in a quantum ballistic channel (QBC). Our calculations show that light absorption in a QBC with a non-uniform narrowed end can lead to a photovoltaic effect. Using mode matching techniques, the photocurrent is obtained. Evaluation of the responsivity, detectivity and bandwidth of the proposed photovoltaic detector is favourable for practical applications

Refereed Proceeding Papers

1. V. Ryzhii and I. Khmyrova. Bistability effect in laser-transistor resonant-tunneling structure. In Workbook of Sixth International Conference on Modulated Semiconductor Structures, pages 992-997, Garmish-Partenkirchen, Germany, Aug. 1993.

   We report laser-bipolar transistor incorporating a resonant-tunneling structure (RTLBT) operation analysis. An analytical model of RTLBT is proposed and used. It is shown that RTLBT can exhibit a bistable operation so that in a certain range of collector voltage the collector and the base currents, and the stimulated photon emission intensity are double-valued. The physical nature of the bistability effect is associated with a mobile electron space charge in the collector that influences the electron transparency of the resonant-tunneling structure and the pumping conditions of the laser active region.

   
   

2. L. Fedichkin, V. Ryzhii, and V. V'yurkov. Novel tunable infrared detector based on a quantum ballistic channel. In Workbook of Sixth International Conference on Modulated Semicond.Structures, pages 922-926, Garmish-Partenkirchen, Germany, Aug. 1993.

   A new tunable far infrared detector based on a quantum ballistic channel in the asymmetric split-gate structure is proposed and considered theoretically. The asymmetric split-gate provides a long constant width channel with a rather sharp asymmetric narrowing at its end. It is supposed that only the lowest 1st subband in a wide channel is occupied by electrons. There is a thick barrier for these electrons in the narrow channel, so the dark current reduces almost to zero. Due to the asymmetric variation of the channel width the electrons can pass the narrow region of the channel under illumination with the photon energy close to subband separation. The Ampere-Watt responsivity of the photovoltaic detector under is evaluated. The advantage of the proposed detector is the possibility of tuning by a gate voltage and small response time.

   
   

3. G. Khrenov, V. Ryzhii, and S. Kartashov. Ensemble Monte Carlo simulation of the hot electron transport in the heterojunction bipolar transitors. In Proceeding of the International Workshop on Computational Electronics, pages 209-213, Leeds, England, Aug. 1993. University of Leeds.

   The effect of the electron transport regime in the base-collector junction on steady-state and high-frequency characteristics of a heterojunction bipolar transistor (HBT) is examined. A new technique based on the Fourier analysis of the induced collector current to evaluate HBT high frequency performance is used. The non-stationary electron transport, velocity overshoot effects and effects of the high-current density are taken into account using self-consistent time-dependent ensemble Monte Carlo particle simulation.

   
   

4. M. Ershov and V. Ryzhii. Electron transport model for unstrained and strained Si and SiGe. In Proceeding of 1993 International Workshop on VLSI Process and Device Modeling, pages 110-111, Nara, Japan, May 1993.

   The realization of the high-quality Si/SiGe heterostructures combined with Si technology opens the possibility for various new device applications. One of the most prominent Si/GeSi-based heterostructure devices is the Si-MOSFET and heterojunction bipolar transistor with a SiGe base. The knowledge of electron transport properties in unstrained and strained Si and SiGe is necessary for the electric characteristics calculation of the above mentioned devices and their structure optimization. In the present work we apply Monte Carlo simulation technique to investigate electron transport characteristics in Si and SiGe strained and unstrained semiconductors and to derive simle their analytical approximations suitable for implementation in device simulation programs.

   
   

5. G. Khrenov, V. Ryzhii, and S. Kartashov. Hot electron in HBT base: Transition from diffusive to nonequilibrium transport. In Technical Digest of 1993 International Conference on VLSI and CAD, pages 412-415, Taejon, Korea, Nov. 1993.

   The influence of the electron transport in the base of a heterojunction bipolar transistor on its steady-state and high-frequency characteristics is investigated by an ensemble Monte Carlo particle method. A new method of HBT high-frequency performance calculation based on the Fourier analysis of the non-stationary current is proposed and implemented. It is found that for the base thickness less than 0.06 mcm the nonequilibrium electron transport in the base causes a base cut-off frequency to vary as the reciprocal of the base thickness in contrast with the prediction of the diffusive theory.

   
   

6. M. Ershov and V. Ryzhii. Simulation of electron transport in strained silicon-carbon alloy. In Proceeding of International Conference on Advanced Microelectronic Devices and Processing, pages 575-578, Sendai, Japan, March 1994. Research Institute of Electrical Com.,Tohoku University.

   Electron transport properties of strained SiC random alloy grown on Si(100) substrate were investigated using Monte Carlo simulation. The value of alloy scattering potential has a strong effect on the low-field electron mobility. The valley repopulation effect can give rise to an increase of in-plane drift velocity with carbon concentration in spite of the enhancement of the alloy scattering. At high electric fields transport parameters tend to the values for pure Si due to electron heating.

   
   

7. G. Khrenov and V. Ryzhii. Doping, barrier parameters and temperature effects in resonant tunneling diodes. In Proceeding of International Conference on Advance Microelectronic Devices and Processing, pages 559-564, Sendai, Japan, March 1994.

   A method to evaluate current-voltage characteristics of the resonant-tunneling diodes based on a self-consistent solution of Poisson and Schroedinger equations is developed. The non-parabolic electron spectrum, charge accumulation and depletion layers are taken into account. The influence of the diode structure parameters on the peak-to-valley current ratio is investigated under different operation conditions.

   
   

8. G. Khrenov, V. Ryzhii, and S. Kartashov. Optimization of the AlGaAs/GaAs HBT structure for high-frequency performance. In Proceeding of International Conference on Advance Microelectronic Devices and Processing, pages 543-548, Sendai, Japan, March 1994.

   A method to evaluate high-frequency performance for heterojunction bipolar transistors based on Fourier analysis of the non-stationary collector current response is proposed. The nonequilibrium electron transport and velocity overshoot effects are taken into account by ensemble Monte Carlo particle simulation. The influence of the emitter and collector capacitances on high frequency performance is also included in our consideration. The parameters of the HBT collector structure are examinated for optimization of the AlGaAs/GaAs HBT high-frequency performance.

   
   

9. V. Ryzhii, I. Khmyrova, and M. Ryzhii. Electrical and optical switching in a bistable bipolar transistor with resonant-tunneling collector structure. In Proceeding of International Conference on Advance Microelectronic Devices and Processing, pages 565-568, Sendai, Japan, March 1994.

   A bipolar heterostructure transistor with resonant-tunneling collector structure (RTBT) is theoretically considered. It is shown that the RTBT can exhibit bistable operation and optical switching. The bistability mechanism is explained by the influence of a mobile electron space charge in the collector region on the electron transport through the resonant-tunneling structure (RTS). The optical switching energy is evaluated.

   
   

10. V. Ryzhii and M. Ershov. Monte Carlo modeling of infrared multiple-quantum-well (MQW) phototransistor. In Technical Digest of International Workshop on Numer.Model.of Processes and Devices for Integr.Circuits:NUPAD V, pages V-67 - V-70, Honolulu, Hawaii, June 1994.

    An infrared multiple-quantum-well (MQW) phototransistor is proposed and considered theoretically. The MQW phototransistor utilizes intersubband optical absorption and exhibits giant photocurrent gain which is due to the thermionic injection of hot electron across the emitter barrier and fast electron transit through the MQW base. We use Monte Carlo simulation to study the hot electron transport effect on the performance of the MQW phototransistor for different base widths and electron injection energies. Transition from near ballistic hot electron transport to diffusive transport decreases the responsivity but its value can be significant in this case as well.

    
    

11. G. Khrenov, V. Ryzhii, and S. Kartashov. A method of heterojunction bipolar transistor high frequency performance calculation. In Technical Digest of International Workshop on Numer.Model.of Processes and Devices for Integr.Circuits:Nupad V, pages V-71 - V74, Honolulu, Hawaii, June 1994.

    A numerical method based on the Fourier analysis of the collector current response to calculate high-frequency characteristics of the heterojunction bipolar transistors is proposed and implemented. The hot electron effects and high current phenomenon are taken into account by ensemble Monte Carlo particle simulation. The experimental results for the cut-off frequency and maximum oscillation frequency are compared with computed results to verify accuracy of the developed method.

    
    

12. M. Ershov and V. Ryzhii. Modeling of infrared multiple-quantum-well phototransistor using Monte Carlo method. In Proceeding of the 1994 IEICE Spring Conference, pages 4-233, Yokohama, March 1994. The Institute of Electronics, Information and Communication Engineers.

    This work deals with the investigation of a multiple-quantum-well (MQW) phototransistors for the infrared region of the spectrum using the Monte Carlo particle method. The performance of the MQW phototransistor, in particular, its responsivity is considered and evaluated.

Academic Activities

1. Irina I. Khmyrova, The Institute of Electrical and Electronics Engineers, March 1994.

   Senior Member.

   
   

2. Irina I. Khmyrova, Third World Organizations for Women in Science, October 1992.

   Associate member.

   
   

3. Gregory Yu. Khrenov, The Institute of Electrical and Electronics Engineers, January 1994.

   Member.

   
   

4. Victor I. Ryzhii, Russian Academy of Sciences, December 1987.

   Corresponding member.

   
   

5. Victor I. Ryzhii, The Institute of Electrical and Electronics Engineers, Inc., October 1993.

   Senior Member.

   
   

6. Victor I. Ryzhii, Japan Society of Applied Physics, November 1993.

   Member.

   
   

7. Victor I. Ryzhii, The Institute of Electronics, Information and Communication Engineers, July 1993.

   Member.

   
   

8. Victor I. Ryzhii, Journal ``Microelectronics'', January 1990.

   Member of Editorial board.

   
   

9. Victor I. Ryzhii, Journal ``Mathematical Modeling'', January 1990.

   Member of Editorial board.

Others

1. V. Ryzhii, G. Khrenov, and M. Ryzhii. Educational program FIELD EFFECT TRANSISTOR, 1994.

   The developed program is a computer visual aid for the course ``Theory of semiconductors''.

   
   

2. V. Ryzhii and M. Ryzhii. Educational program PHOTODIODES, 1994.

   The developed program is a computer visual aid for the course ``Theory of semiconductors''.

   
   

3. Victor I. Ryzhii. Grant from the Fukushima Prefecture Foundation for the Promotion of Science and Education. Simulation and design of microelectronic and nanoelectronic devices, 1994.