Etude et simulation d’un transistor opto-hyperfréquence InP/InGaAs.

Abstract

This thesis work is part of a study of a heterojunction bipolaire phototransistor (HPT) NPN InP/InGaAs. The phototransistor is modelled using a numerical method, and the results are presented and discussed. This model is based on heterojunction bipolar transistor (HBT) model with the consideration of the optical beam effect. The physical model used in the numerical simulation is the drift diffusion where we applied the finite difference method. In this work, we have realyzed two types of numericals simulations for The NPN InP/InGaAs heterojunction phototransistor (HPT). In the first part, To better understand the functioning principle of this component under an external base bias current, we have compared the simulated electrical characteristics for low and high base bias current for different incident optical powers. These results show that under a higher base bias current, lower values of optical power can give high injection (Kirk effect) in a phototransistor. This value increases with decreasing base bias current. For IB = 5 µA, the optical power value which can give high injection is three times higher than this for IB = 100 µA. The HPT is suitable for detecting signals as a front-end receiver at very low optical input powers because of its very high sensitivity. In the second part, we presented the impact of the base thicknesson the electrical and optical characteristics of the HPT NPN InP/In0.53Ga0.47As.The results show that responsivity and optical gain are not only strongly dependent on the base thickness but also on the base current. The increasing of the current gain from 60 to 100 as the base was scaled from 60 down to 20 nm. Responsivity of 14.7 A/W for 1100 nm light is achieved when the thickness of base layer is 20 nm. A good qualitative agreement of the numerical and analytical simulated value of responsivity as a function of the wavelength with the existing experimental data was achieved.