Improvement of CdTe passivation by vacuum evaporation on HgCdTe infrared focal plane arrays

Deposition in thermal ambience can obtain better CdTe passivation layers compared with general evaporation process. HgCdTe infrared focal plane arrays are fabricated to confirm the new process works well. Contrast n(+)-on-p planar photodiodes are manufactured from the same HgCdTe epilayer. Some use new process while others use general process. The performance of devices using new process shows a significant improvement. The device with general passivation process has a dark current of 7.8x10(-7) A at 50 mV negative bias voltage, and the differential resistance at zero bias is 2.6x10(5) Omega. Meanwhile, the device with new passivation process has a dark current of 1.7x10(-8) A at 50 mV negative bias voltage, and the differential resistance at zero bias is 8.0x10(5) Omega. Moreover, this new heating process provides a better thermal stability. The performance of devices with general passivation process declines after a long time baking at 70 degrees C. But the performance of the devices with heating passivation process improves a little after a long time baking even at 80 degrees C. The results show that CdTe deposition by vacuum evaporation in a thermal ambience can make a good HgCdTe surface passivation protection.