A HETEROJUNCTION MINORITY-CARRIER BARRIER FOR INSB DEVICES

We describe the properties of heterostructure InSb/ln1-xAlxSb diodes grown by molecular beam epitaxy, The leakage current in a homostructure InSb p+ pi n+ diode at room temperature is dominated by an electron current which is generated in the p+ material. We show that a thin strained layer of In1-xAlxSb grown between the p+ and pi regions produces a barrier in the conduction band which reduces substantially the diffusion of electrons from the p+ layer to the pi region, and hence to the diode junction, leading to an improvement in performance. We present experimental results which show that the saturation leakage current reduces by over an order of magnitude as the aluminium composition in the barrier is increased, provided that it remains strained. The effect on device performance of exceeding the critical thickness for strain relief is also demonstrated. The experimental data are compared with analytic and numerical models, and factors which determine the optimum barrier composition, thickness and doping are discussed.