Investigation On Transport Properties Of Ⅲ-Ⅴ Nitride Semiconductor Based On Monte Carlo Method

In recent years, with the progress of III-V nitride semiconductor growth techniques,nitride-based III-V compound semiconductor devices exhibit more and more excellentperformance, and gradually enter the applications. For the reason, the correspondingtransport studies have received wide attention. To accurately model and predict theperformance of III-V semiconductor device, the transport properties of III-V nitridesemiconductor need to be researched. What’s more, the key parameters, like mobilityand diffusion coefficient, need to be modeled. Since the III-V nitride semiconductoroften work under conditions of strong field and high-frequency, in order to be able toaccurately describe its transport properties, the Monte Carlo method is widely used todo the research on their transport studies. In this dissertation, the transport properties ofIII-V nitride semiconductor materials have been systematically studied and the mainresearch results are as follows.1, A transport platform which can do the simulation of III-V nitride semiconductortransport properties has been developed. For scattering properties of III-V nitridesemiconductors, based on ensemble Monte Carlo method, developing a platform, whichcan do the transient and steady state simulation of semiconductors. Finally, by couplingthe Monte Carlo method and the Poisson equation, a simulator which is used to doone-dimensional semiconductor device simulation is constructed.2, Transient transport properties of III-V nitride semiconductors have been studied.Based on Monte Carlo transport platform, transient transport, energy and momentumrelaxation process of Wurtzite InN are studtied. With the help of relaxation study, thephysical mechanisms of negative differential mobility in steady-state transport aresystematically studied. For the anisotropic characteristics of electronic structure in InN,the anisotropic transport properties have been studied. For wurtzite and zinc blendeInN，the velocity undershoot has been researched which is seldom studied for the pastyears. Finally, the speed overshoot and undershoot in wurtzite GaN phenomena issimulated.3, The momentum and energy relaxation processes of III-V nitride semiconductorsare studied systematically studied, which has not been studied at present during thetransport study on III-V nitride semiconductors. To meet the requirements of the energybalance equation for relaxation time model, momentum and energy relaxation processes of wurtzite GaN, InN and AlN are studied to obtain the momentum and energy electronrelaxation time vs. temperature, which can be used to establish the momentum andenergy model. Meanwhile, the effects of doping concentration on the momentum andenergy relaxation times have been studied and the work shows that in order to establishan accurate analytical model of momentum and energy relaxation times, the impact ofthe doping concentration must be considered.4, The steady-state transport properties of III-V nitride semiconductors have beenstudied. For the current status of the lack of research on the diffusion coefficient in III-Vnitride semiconductor transport study, based on Monte Carlo, time correlation functionand the second central moment method, the diffusion coefficient of wurtzite GaN andInN were studied and a clear relation between the diffusion coefficient with the electricfield, temperature, doping concentration and frequency are established. Based onEinstein’s equations and diffusion coefficients, an anisotropic analytical mobility modelof wurtzite InN are established, which can be used in device simulation software.Furthermore, the high-field transport propertied of wurtzite InN was studied, which cabbe used to construct analytical high field mobility model.5, The transport propertied of uniform doping Gunn diode is studied, which is used asthe terahertz source. Based on Monte Carlo method and the Poisson equation, atterahertz frequencies, in the DC and AC bias, their transport behavior has been studiedto produce clear physical mechanism Gunn oscillation for uniformly doped GaN Gunndiode. Our research has shown that current may not increase when the accumulationdomain moves to the anode, the average carriers speed within the device play a moreimportant role than electron concentration. The study also showed that the Monte Carlomethod is need to accurately describe the carrier transport behaviors of THz sourcebased on Gunn diode and the traditional drift-diffusion model can not accuratelydescribe their electronic transport properties and the mechanism of Gunn diode underTHz frequency.