MONTE CARLO SIMULATION OF EXCESS NOISE IN HETEROJUNCTION AVALANCHE PHOTODETECTOR

摘要

Avalanche photodetectors (APDs) are important optoelectronic devices used in the detection of very low optical signals in fibre-optic communication systems. The advantage of high gain mechanism through carrier multiplication in materials is exploited in designing the APDs. However, a price has to pay in terms of the associated multiplication noise. The excess noise referring to the multiplication fluctuation is quite prominent if the ratio of the ionization coefficients of the electrons and holes approach towards unity. Low noise APDs can be realized if the two ionization coefficients differ widely with each other. The band discontinuity at the heterointerface greatly deviates the ratio from unity and thereby realizing the possibility of fabricating low noise heterostructure APDs. Recently models have been proposed [1] to simulate the multiplication, ionization and excess noise for p{sup}+-i-n{sup}+ homojunction photodiodes and also GaAs/AlGaAs heterojunction diodes. The use of random path length (RPL) model in the framework of Monte-Carlo (MC) method has proved to yield results in agreement with the observed experimental values. The heterostructure InP/InGaAs APD has been reported for use in the 1-1.6 μm. wavelength for fibre-optic communication [2]. This material system has yet to be paid proper attention to extract its potential values. In the paper, the avalanche effect in this relatively less studied material system is made in the RPL model and simulating the results in the framework of MC formalism. The technique of using the model is very similar to that used in ref. [1].