Molecular Beam Epitaxy of Sb-based Semiconductors

Abstract

The growth of semiconductor antimonides by molecular beam epitaxy (MBE) was first reported in the late 1970`s. In recent years, the emergence of several potential device applications has resulted in increased activity in the field. Much of the work focuses on GaSb and AlSb because they are nearly lattice-matched to each other and to InAs (a{sub 0},AlSb = 6.1355 A, a{sub 0}, GaSb = 6.0954 A, a{sub 0}, InAs = 6.0584 A). These semiconductors are often referred to as the `6.1 A family.` Ternaries such as In{sub (x)}Ga{sub 1{minus}x}Sb, AlAs{sub x}Sb{sub 1{minus}x}, and GaAs{sub x}Sb{sub 1{minus}x} also have lattice constants close to 6.1 A if x is small. The interest in 6.1 A materials is based upon the wide range of available band alignments and band gaps. These are illustrated in a figure. For example, InAs is a small band gap semiconductor (e.g., 300K = 0.36 eV) with a small electron effective mass (m{sub e} = 0.023m{sub 0}) and large room-temperature mobility (30,000 sq cm/V-s). Hence, it is a candidate for the channel material in high-speed field-effect transistors (FETs). AlSb is an indirect-gap semiconductor with a large band gap (1.63 eV). The conduction band offset between AlSb and InAs ismore » 1.35 eV, making AlSb a potential barrier material for FETs. A second example is InAs/GaSb. The band alignment is type-II, with the GaSb valence band lying above the InAs conduction band. Short-period superlattices formed with InAs and GaSb have small, tunable energy gaps and high absorption coefficients. Hence, they are candidates for long-wavelength infrared detectors.« less