Abstract
Heterovalent structures consisting of group II-VI/group III-V compound semiconductors offer attractive properties, such as a very broad range of bandgaps, large conduction band offsets, high electron and hole mobilities, and quantum-material properties such as electric-field-induced topological insulator states. These properties and characteristics are highly desirable for many electronic and optoelectronic devices as well as potential condensed-matter quantum-physics applications. Here, we provide an overview of our recent studies of the MBE growth and characterization of zincblende II-VI/III-V heterostructures as well as several novel device applications based on different sets of these materials. By combining materials with small lattice mismatch, such as ZnTe/GaSb (Δa/a ∼ 0.13%), CdTe/InSb (Δa/a ∼ 0.05%), and ZnSe/GaAs (Δa/a ∼ 0.26%), epitaxial films of excellent crystallinity were grown once the growth conditions had been optimized. Cross-sectional observations using conventional and atomic-resolution electron microscopy revealed coherent interfaces and close to defect-free heterostructures. Measurements across CdTe/InSb interfaces indicated a limited amount (∼1.5 nm) of chemical intermixing. Results for ZnTe/GaSb distributed Bragg reflectors, CdTe/MgxCd1−xTe double heterostructures, and CdTe/InSb two-color photodetectors are briefly presented, and the growth of a rock salt/zincblende PbTe/CdTe/InSb heterostructure is also described.
Highlights
The concepts of heterostructures[1] and artificial superlattices[2] have created a vast panorama for semiconductor physics featuring novel low-dimensional phenomena, such as quantum confinement, Bloch oscillations,[3] and the fractional quantum Hall effect.[4,5]. These developments were enabled by the emergence of molecular beam epitaxy (MBE),[6] and they have spurred the invention of many novel types of electronic devices, such as high electron mobility transistors,[7] quantum cascade lasers (QCLs),[8] type-II superlattice infrared (IR) photodetectors,[9] and quantum-well IR photodetectors (QWIPs).[10]
The oxide layers on undoped GaSb (100) substrates were first thermally desorbed at 500 °C in the III-V chamber under Sb flux with a beam equivalent pressure (BEP) of ∼1.6 × 10−6 Torr, followed by growth of a thin (∼20 nm) GaSb buffer layer at 480 °C using a dual-chamber MBE system in Furdyna’s group at Notre Dame University, with similar cell configurations as shown in Fig. 2.19 The substrate temperatures were usually measured using a thermocouple on the back of the substrate holder, which had been previously calibrated using a pyrometer
Realizing optimum growth conditions needs to account for large differences in growth temperature as well as vapor pressures for the II-VI versus III-V constituents
Summary
The concepts of heterostructures[1] and artificial superlattices[2] have created a vast panorama for semiconductor physics featuring novel low-dimensional phenomena, such as quantum confinement, Bloch oscillations,[3] and the fractional quantum Hall effect.[4,5] These developments were enabled by the emergence of molecular beam epitaxy (MBE),[6] and they have spurred the invention of many novel types of electronic devices, such as high electron mobility transistors,[7] quantum cascade lasers (QCLs),[8] type-II superlattice infrared (IR) photodetectors,[9] and quantum-well IR photodetectors (QWIPs).[10]. Our recent research has been directed toward heterostructures that combine members of the II-VI family (BeMgZnCd)(SeTe) and the III-V family (AlGaIn)(NPAsSbBi), which can be grown on many commercially available semiconductor substrates, such as GaN, Si, Ge, GaAs, InP, InAs, GaSb, and InSb. these materials (including type-II superlattices) have bandgaps that span the entire wavelength spectrum from far-infrared to near-ultraviolet. This platform of heterovalent materials provides extra capabilities that are not achievable with the conventional families of isovalent heterojunctions. We provide an overview of our recent research, which has been directed toward the growth and characterization of these lattice-matched families of II-VI/III-V heterostructures, as well as exploring several related device applications
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