Current transport characteristics of P+/N AlxGa1−xAs homojunction diodes

This paper reports a current transport study on the P+/N AlxGa1−xAs homojunction diodes with the AlAs mole fraction, x, ranging from 0 to 0.66. From the 2-kT surface recombination current behavior, the surface state density is nearly independent of x as x is smaller than 0.2. On the other hand, as x is larger than 0.2, the surface state density decreases as x increases. A photocurrent-aided method is proposed to extract the embedded 1-kT current out of the series resistance effect. It is found that the 1-kT current follows Shockley diffusion theory, and the hole diffusion length has a drastic change in the transition region from direct to indirect band. A three-band diffusion model considering the Γ-band-electron-concentration-dependent hole lifetime has been proposed to explain the experimental results successfully.