Potential barriers in HgCdTe heterojunctions

The graded energy gap heterojunction in HgCdTe is analyzed using a highly accurate computer model that solves the one-dimensional semiconductor equations. Results are shown in the form of energy band diagrams which illustrate several important features expected to be encountered in these heterojunctions. In particular, our calculations demonstrate the existence of potential energy barriers to minority carrier transport in the conduction band of wide-gap-n on narrow-gap-p structures and in the valence band of wide-gap-p on narrow-gap-n structures. Also demonstrated are cases where these barriers are eliminated. The physics of barrier formation is discussed in terms of the internal force fields due to the electrostatic potential gradient in the depletion region of the p-n junction and the gradient of electron affinity in the graded gap region of the heterojunction. Results obtained from computer simulations were found to be in qualitative agreement with previous experimental data on HgCdTe heterojunctions.