LAUSR

The NPN InP/InGaAs heterojunction phototransistor (HPT) is numerically simulated with a two dimensional model based on a finite difference method. The electrical and optical characteristics of HPT are analyzed with different base thickness and compared as the base was scaled from 60 down to 20 nm. The impact of the base thickness on the photocurrent is highlighted and compared with the dark and the photodiode currents. This paper also includes the effect of optical power and base current on the potential, electrons density and energy band diagrams. 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.