Study On Noise Characteristic Of Thin Multiplication Region APD And Carriers Transport In Semiconductor

Avalanche photodiodes are the detector of choice in many high-speed lightwavesystem mainly due to their internal optoelectronic gain, this gain is, however, accompaniedby excess noise arises from randomness in the coupled avalanching process.Semieonductor material is one of the most useful solid materials, the research of thetransport proeess of carrier can help to disclose the microscopic process in semiconductormore deeply and know the material characteristics more clearly. Monte Carlo method hasbeen widely used to study the carrier transport properties of semiconductor devices. It is astatistical probability method, which solves physics problems using statistical numericaltheory. It’s an effcetive way to simulate the nonlocal transport proporties of semiconductormaterials and small size devices. The main content includes the following two parts:1. The study of noise characteristics of avalanche photodiodes with thinmultiplication-regions. The conventional McIntyre carrier multiplication theory foravalanche photodiodes (APD’s) does not adequately describe the experimental resultsobtained from APD’s with thin multiplication-regions, incorporating dead space in themodel resolves the discrepancy. The dead space is the minimum distance a carrier musttravel before acquiring sufficient kinetic energy enabling it toimpact ionize. Recurrencerelations in the form of coupled linear integral equations are derived to characterize theunderlying avalanche multiplication process. Numerical solutions to the integral equationnsare obtained. The ionization coefficients of enabled carriers that have traveled the deadspace are determined as functions of the electric field, within the confines of a singleexponential model for each device, independent of multiplication-region width. The modelparameters are determined directly from experimental data. The use of these physicallybased ionization coefficients in the dead-space multiplication theory, provides excess noisefactor versus mean gain curves that accord very closely with those measured for each device, regardless of multiplication-region width. It is verified that the ratio of thedead-space to the multiplication-region width increases, for a fixed mean gain, as the widthis reduced. This behavior, too, is in accord with the reduction of the excess noise factorpredicted by the dead-space multiplication theory. It has been shown that the noisecharacteristics of avalanche photodiodes (APDs) can greatly benefit from the presence ofmoderate amounts of an initial energy stored in the injected carriers that initiate theavalanche multiplication process. The key mechanism for the improved performance is thesignificant reduction of the first dead space in the ionization process. The reduction of thefirst dead space has the effect of localizing the first impact ionization and forcing it to occurquickly near the edge of the multiplication region. A theoretical model for the avalanchemultiplication is utilized to examine the fundamental limits of excess noise in light of theinitial-energy effect in practical APD structures.2. Constructing a semiconductor simulation platform by using Monte Carlo method,and using the platform to study the transport properties of bulk InP and bulk GaN.This partpresents a detailed introdction of the Monte Carlo method and an intrsystematic theoreticalMonte Carlo simulation mode.The ionized impurity,polar optical phonon, acoustic phonon,piezoelectric, and intervralley seattering mechanisms are discucssed, as well as thenonparabolicity is considered in three valleys. Then a Monte Carlo simulation platform isconstructed using Matlab in Windows, using this platform transport properties of bulk InPand bulk GaN are studied. The results we obtained give further explanations of Ⅲ-Ⅴcompound semiconductor transport phenomena, and are meaningful in designingsemiconductor devices.