Metal-Organic Chemical Vapor Deposition of Hg_1−x Cd _x Te Fully Doped Heterostructures Without Postgrowth Anneal for Uncooled MWIR and LWIR Detectors

Uncertainty in precursor pulse delays and shapes has been found to be an important factor in Hg_1−x Cd _x Te metal-organic chemical vapor deposition (MOCVD) growth using the interdiffused multilayer process (IMP). Herein, metal-organic concentration changes in the growth zone are examined using an in␣situ infrared (IR) absorption gas monitoring system, and modifications to the interdiffused multilayer process are applied for in␣situ control of stoichiometry, improved morphology, minimized process length, and consumption of precursors. Dimethylcadmium (DMCd) introduction during IMP flush stages in HgTe was used for stoichiometry control. The final stage of heterostructure formation was optimized to prevent Hg outdiffusion. As a result, vacancy concentration was reduced far below the equilibrium level at the growth conditions so the background of n-type doping was revealed. Acceptor doping with arsine (AsH₃) and trisdimethylaminoarsenic (TDMAAs) was examined over a wide range of compositions, and doping levels of 5 × 10¹⁵ cm⁻³ to 5 × 10¹⁷ cm⁻³ were obtained. The presence of both arsenic dopants significantly increased the CdTe growth rate. This caused an increase of Cd mole fraction in the grown material. Doped heterostructures can be grown without any postgrowth anneal and used for mid- and long-wavelength infrared (MWIR and LWIR) devices operating at near-ambient temperatures.