Liquid-Phase Epitaxy of Hg1−xCdxTe from Hg Solution: A Route to Infrared Detector Structures

Abstract

ABSTRACTOver the past few years, liquid-phase epitaxy (LPE) has become an established growth technique for the synthesis of HgCdTe. This paper reviews one of the most successful LPE technologies developed for HgCdTe, specifically, “infinite-melt” vertical LPE (VLPE) from Hg-rich solutions.Despite the very high Hg vapor pressure (> 10 atm) and the extremely low solubility of Cd in the Hg solution (< 10−3 mol%), this approach was believed to offer the best long-term prospect for growth of HgCdTe suitable for various device structures. Since the initial demonstration of LPE growth of HgCdTe layers from Hg solution in experiments conducted at SBRC in 1978, the VLPE technology has advanced to the point where epitaxial HgCdTe can now be grown for photoconductive (PC) and photovoltaic (PV) as well as monolithic metal-insulator-semiconductor (MIS) and high-frequency laser-detector devices with state-of-the-art performance in the entire 2–12 μm spectral region.A historical perspective and the current status of VLPE technology are reported. Particular emphasis is placed on the important role of the ther-modynamic parameters (phase diagram) and on control of stoichiometry (defect chemistry) and impurity doping (distribution coefficient) for growth of HgCdTe layers from Hg solution. Critical material characteristics, such as transport properties, minority-carrier lifetime, morphology and crystal structure, are also discussed. Finally, a comparison with the LPE technol-ogy using Te solutions, which has been the mainstay of the remainder of the IR community, is presented.