p‐type arsenic doping of CdTe and HgTe/CdTe superlattices grown by photoassisted and conventional molecular‐beam epitaxy

In this paper we report on p‐type arsenic doping of CdTe and HgTe/CdTe superlattices by photoassisted and conventional molecular‐beam epitaxy (MBE). We also report on some of the problems involved in doping and growing the HgTe/CdTe superlattice system by theoretically examining two key aspects of its growth: (i) growth of CdTe at low temperatures under Cd‐stabilized conditions, and (ii) effect of laser excitation on the growing CdTe surface. p‐Type arsenic‐doped CdTe and HgTe/CdTe superlattice epilayers were grown on (100) CdTe and CdZnTe substrates at low temperatures under cation‐stabilized conditions obtained either with excess Cd, or excess Hg fluxes. As‐grown arsenic‐doped CdTe layers had room temperature carrier concentrations in the 1014–1016 cm−3 range, and hole mobilities of about 35–65 cm2/V s. Low‐temperature photoluminescence spectra of arsenic‐doped CdTe epilayers grown by photoassisted MBE showed an emission peak at 1.51 eV, which is associated to the AsTe acceptor (arsenic occupying a Te site) with a 92 meV ionization energy. CdTe epilayers grown at low temperatures with photoassisted MBE have superior structural, optical, and electrical properties than those grown by conventional MBE. Arsenic doping of the HgTe/CdTe superlattice structure has resulted in in situ growth of p‐type modulation‐doped superlattices with enhanced mobilities. Undoped superlattices grown under the same conditions are n‐type. These results represent a significant step towards the in situ fabrication of photodiodes and other advanced devices based on HgTe/CdTe doped superlattice structures.