HgCdTe p-on-n Focal-Plane Array Fabrication Using Arsenic Incorporation During MBE Growth

Abstract

Extrinsic p-type doping during molecular-beam epitaxy (MBE) growth represents an essential generic toolbox for advanced heterostructures based on the HgCdTe material system: PiN diodes, mesa avalanche photodiodes (APD) or third-generation multispectral focal-plane arrays. Today, arsenic appears to be the best candidate to fulfill this role and our group is actively working on its incorporation during MBE growth, using an original radio frequency (RF) plasma source for arsenic. Such a cell is supposed to deliver a monatomic As flux, and as expected we observed high As electrical activation rates after annealing short-wave (SW), mid-wave (MW), and long-wave (LW) layers. At last, a couple of technological runs have been carried out in the MW range in order to validate the approach on practical devices. p-on-n focal-plane arrays (FPA) have been fabricated using a mesa delineated technology on an As-on-In doped metallurgical heterojunction layer grown on a lattice-matched CdZnTe layer (320 9 256, 30 lm pitch, 5 lm cutoff at 77 K). Observed diodes exhibit very interesting electro-optical characteristics: large shunt impedance, high quantum efficiency, and no noticeable excess noise. The resulting focalplane arrays were observed to be very uniform, leading to high operabilities. Noise equivalent temperature difference (NETD) distributions are very similar to those observed with the As ion-implanted p-on-n technology, fabricated in our laboratory as well. In our opinion, those excellent results demonstrate the feasibility of our MBE in situ arsenic doping process. Good electrical activation rates and high-quality layers can be obtained. We believe that such an approach allows precise control of the p-doping profile in the HgCdTe layer, which is necessary for advanced structure designs.

Study of LWIR and VLWIR Focal Plane Array Developments: Comparison Between p-on-n and Different n-on-p Technologies on LPE HgCdTe

“…This effect has been already observed in our laboratory on other heterostructures grown, for example, by MBE. 10 However, another hypothesis might also be considered. As mentioned before, p/n diode fabrication requires low n doping level (1.5 9 10 15 cm 3 in the case of Fig.…”

Planar n-on-p HgCdTe FPAs for LWIR and VLWIR Applications

“…Use of n-type MCT, which is virtually without SR centers, as an absorber for p-on-n detectors. Thus, the minority-carrier lifetime should be Auger 1 limited in a p-on-n detector in either mesa [4][5][6][7] concentration for n-on-p detectors in planar 10,11 or lateral collection 12 configuration, where minority-carrier lifetime should be limited by Auger 7 recombination.…”