METALORGANIC CHEMICAL-VAPOR-DEPOSITION OF HGCDTE P N JUNCTIONS USING ARSENIC AND IODINE DOPING/

We report new results on metalorganic chemical vapor deposition (MOCVD ) in situ growth of long wavelength infrared (LWIR) P-on-n and medium wavelength infrared (MWIR) n-on-P HgCdTe heterojunction photodiodes us ing the interdiffused multilayer process (IMP). The n-type regions are doped with iodine using the precursor ethyl. iodide (EI). I-doped HgC dTe using EI has mobilities higher than that obtained on undoped backg round annealed films and are comparable to LPE grown In-doped HgCdTe. The p-type layers are doped with arsenic from either tertiarybutylarsi ne (TBAs) or a new precursor, tris-dimethylaminoarsenic (DMAAs). The s ubstrates used in this work are lattice matched CdZnTe oriented (211)B or (100)4 degrees-->[110]. Junction quality was assessed by fabricati ng and characterizing backside-illuminated arrays of variable-area cir cular mesa photodiodes. This paper presents four new results. First, c arrier lifetimes measured at 80K on arsenic doped single HgCdTe layers are generally longer for films doped from the new precursor DMAAs tha n from TBAs. Second, we present data on the first P-on-n HgCdTe photod iodes grown in, situ with DMAAs which have R(0)A products limited by g -r current at 80K for lambda(infinity) = 7-12 mu m, comparable to the best R(0)A products we have achieved with TBAs. Third, we report the f irst experimental data on a new HgCdTe device architecture, the n-on-P heterojunction, with a wide gap p-type layer which allows radiation i ncident through the substrate to be absorbed in a narrower gap n-type layer, thereby eliminating interface recombination effects. With the n -on-P architecture, MWIR photodiodes were obtained reproducibly with c lassical spectral response shapes, high quantum efficiencies (70-75%) and R(0)A products above 2 x 10(5) ohm-cm(2) for lambda(infinity) = 5. 0 mu m at 80K. Fourth, we report 40K data for LWIR P-on-n HgCdTe heter ojunction photodiodes (using TBAs), with R(0)A values of 2 x 10(4) ohm -cm(2) for lambda(infinity) = 11.7 mu m and 5 x 10(5) ohm-cm(2) for la mbda(infinity) = 9.4 mu m. These are the highest R(0)A values reported to date for LWIR P-on-n heterojunctions grown in situ by MOCVD.