Molecular beam epitaxy has been used to prepare multiple quantum well structures of CdTe/Cd1−xMnxTe on (001) InSb substrates. The growth of such a system on InSb allows the use of particularly low growth temperatures, hence minimizing interdiffusion effects. This study presents the first transmission electron microscope investigation of this multilayer system grown on InSb. The work clearly demonstrates that multiple quantum wells of high structural quality can be grown reproducibly over a wide range of layer thicknesses. The importance of efficient substrate surface cleaning prior to growth is demonstrated. In order to grow high structural quality multilayers, the choice of buffer layer is also important and a possible explanation for this observation is given.

Structure of CdTe‐Cd1−xMnxTe multiple quantum wells grown on (001) InSb substrates by molecular beam epitaxy

Electrical and structural assessment of CdTe and CdMnTe layers grown by MBE on InSb substrates

Large gap II–VI semiconductors have direct band gaps with gap energies ranging from 3.84 (ZnS) to 1.44 eV (CdTe) at RT. They promise optoelectronic devices operating in the visible spectral range. However, a large number of defects and difficulties in preparing n- and p-type material have hampered a broad application. New epitaxial growth methods such as MOVPE and MBE offer a chance to overcome many of these problems and even make a controlled doping possible. The present paper summarizes some aspects of the recent development for ZnS, ZnSe, ZnTe and a few ternary compounds.

Preparation and optical properties of wide gap II–VI compounds

Single and multiple layers of CdTe and CdMnTe have been grown by MBE on InSb substrates. Considerable attention has been given to the preparation of the substrate surface which was cleaned under vacuum using a series of argon ion etching and thermal annealing cycles, with progress being monitored by AES and RHEED. The subsequently deposited epilayers were grown, typically, at a rate of 0.5 mu m per hour. All undoped films studied so far have been found to be n-type with carrier concentrations in the range 1014-1015 cm-3, while layers doped with indium have exhibited a saturation in carrier concentration as the In atom concentration was increased, due to the generation of compensating acceptor states.

H.H. Sutherland

Papers

MBE growth of CdTe and Cd1−xMnxTe layers and multilayers on InSb substrates