Photo-n-p Junctions in ZnTe

We have demonstrated ZnTe devices with efficient (about 1%) light emission at 77 °K in which the injection mechanism is a forward-biasd photo-n-p junction. In one, Al and Cd are diffused into highly p-type ZnTe:P to produce an Al-doped region 70 µm deep with a 20 µm surface layer of average composition Zn
0.6
Cd
0.4
Te. Light emission (575 nm) is observed for 2.5 V. Similar results are obtained when Al alone is diffused in from an evaporated layer to a depth of about 50 µm. This latter device was earlier thought to operate by avalanche injection. Both structures with In contacts to the Al layer give open-circuit photovoltages of over 1.8 V at 77 °K. The all-ZnTe device, however, requires over 7 V to sustain light emission. While it is possible that efficient ZnTe devices made by vapor diffusing the Al are avalanche injection structures, efficient avalanche injection in a II–VI device has yet to be conclusively demonstrated.