Single Crystal Compound Semiconductors Research Articles

Low Temperature Growth of Crystalline Semiconductors on Nonepitaxial Substrates

AbstractIn this work, a low temperature templated liquid phase (LT‐TLP) growth process is presented, that enables one to directly grow high optoelectronic quality single crystalline compound semiconductors (InP and InAs) on amorphous dielectrics at temperatures below 400 °C. Uniquely, the material quality is optimal when InP is grown at 300 °C, a temperature which is low enough to enable back‐end‐of‐line growth on fully fabricated Si complementary metal oxide semiconductor circuits. Using this low‐temperature grown InP, a transistor fabrication process is then entirely carried out at 300 °C or below, and an indium phosphide nanoribbon field effect transistor with excellent on/off ratios is demonstrated, indicating low defect density in the material. Overall, this approach enables growth of large area (tens of micron) single crystal compound semiconductor at low temperatures, establishing a back‐end‐of‐line (BEOL) compatible process for monolithic 3D device integration.

Perovskite nanostructures: Leveraging quantum effects to challenge optoelectronic limits

Metal halide perovskites have affirmed their pedigree as extraordinary semiconducting materials, exhibiting properties rivalling those observed in single crystal compound semiconductors. Perovskites show tremendous versatilities in both structure and composition tuning, and therefore applications ranging from optoelectronics to X-ray imaging and spintronics, neuromorphic electronics are emerging. Moreover, when their dimensions become comparable to the exciton Bohr radius, perovskite nanostructures and layered systems display remarkable properties because of quantum confinement. Nanostructured and lower dimensional layered perovskites exhibit properties that are yet to be fully exploited such as extraordinarily high luminescence, narrow emissions, high exciton binding energies, strong non-linear phenomena, and carrier cascade characteristics. This review, while highlighting the frontier phenomena that continue to be unravelled, outlines how confined structures of these materials have demonstrated properties that promise to unlock exceptional quantum phenomena to challenge the optoelectronic limits.

Absorption-edge anisotropy of Cu 2ZnSiQ 4 (Q = S, Se) quaternary compound semiconductors

Polarization-dependent absorption characterization of Cu 2ZnSiQ 4 (Q = S, Se) quaternary single crystal compound semiconductors were carried out in the temperature range of 10–300 K. The absorption measurements were performed on the as grown basal plane with the normal along [2 1 0] and the axis c parallel to the long edge of the crystal platelet. A significant shift towards lower energy was observed in the absorption spectra of E⊥ c polarization with respect to those corresponding to E∥ c polarization. A comprehensive analysis of the absorption spectra revealed that the absorption edges of the studied crystals are indirect allowed transitions. A schematic representation of the plausible assignments for the observed near band edge optical transitions for Cu 2ZnSiQ 4 was proposed. The variation of the indirect transition energies with temperature were analyzed by Varshni and Bose–Einstein expressions. The parameters that describe the temperature dependence of the indirect transition energies with different polarizations were evaluated and discussed.

Massive point defect redistribution near semiconductor surfaces and interfaces and its impact on Schottky barrier formation

Abstract Nanoscale depth-resolved cathodoluminescence spectroscopy calibrated with deep level transient spectroscopy of native point defects and capacitance–voltage measurements of free carrier densities, all at the same metal–semiconductor interface, demonstrate that native point defects can (i) increase by order-of-magnitude in densities with tens of nanometers of the semiconductor surface, (ii) alter free carrier concentrations and band profiles with the surface space charge regions, and (iii) dominate the Schottky barrier formation for metal contacts to ZnO and many other single crystal compound semiconductors. The spatial redistribution of electrically active defects within the surface space charge can be understood in terms of temperature-dependent atomic diffusion enabled by low formation energies and driven by strain and electric fields as well as metal-specific chemical reactions near room temperature, consistent with first-principles calculations of interfacial segregation and migration barriers. These results underscore the importance of native point defects in charge transport and barrier formation at semiconductor interfaces.

Direct Growth of Compound Semiconductor Nanowires by On-Film Formation of Nanowires: Bismuth Telluride

Bismuth telluride (Bi(2)Te(3)) nanowires are of great interest as nanoscale building blocks for high-efficiency thermoelectric devices. Their low-dimensional character leads to an enhanced figure-of-merit (ZT), an indicator of thermoelectric efficiency. Herein, we report the invention of a direct growth method termed On-Film Formation of Nanowires (OFF-ON) for making high-quality single-crystal compound semiconductor nanowires, that is, Bi(2)Te(3), without the use of conventional templates, catalysts, or starting materials. We have used the OFF-ON technique to grow single crystal compound semiconductor Bi(2)Te(3) nanowires from sputtered BiTe films after thermal annealing at 350 degrees C. The mechanism for wire growth is stress-induced mass flow along grain boundaries in the polycrystalline film. OFF-ON is a simple but powerful method for growing perfect single-crystal compound semiconductor nanowires of high aspect ratio with high crystallinity that distinguishes it from other competitive growth approaches that have been developed to date.

Luminescence studies of semiconductor electrodes

In this paper we review our recent results of in-situ luminescence studies of semiconductor electrodes. Three classes of materials are considered: single crystal compound semiconductors, porous silicon and semiconducting oxides doped with luminescent ions. We show how photoluminescence (PL) and electroluminescence (EL) measurements can give information about the optical and optoelectrical properties of the solid and about mechanisms of surface reactions. The relevance of time- and frequency-dependent measurements, which have been largely neglected, is stressed.

Crystal-face specific electrochemical effects on cadmium sulphide

The energetics of a semiconductor/electrolyte interface are conditioned by the crystallography of the surface presented to the electrolyte. The effect is particularly significant for anisotropic single crystal compound semiconductor photoelectrochemistry. The relevant interface parameters for single crystal n-type cadmium sulphide photoanodes in contact with electrolytes are investigated. The significant influence of dissolved oxygen in the electrolyte is noted.

Recent Advances in Sputter Deposition

This paper has two objectives. One is to review some of the essential features of the sputtering process. The second is to discuss several recent developments relating to the use of reactive sputtering for the deposition of oxide and semiconductor compounds and to the use of controlled substrate ion bombardment for the purpose of modifying coating properties. The particular topics include: (i) a magnetic field configuration that facilitates controlled substrate ion bombardment in planar magnetron sources; (ii) the use of baffelled targets and substrate ion bombardment for improving composition control during the reactive sputter deposition of metal oxides; (iii) the use of substrate temperature to assist in controlling the stoichiometry of semiconducting CuInSe2 coatings deposited by reactive cosputtering; and (iv) the use of ion bombardment to neutralize surface reactions and permit metastable single crystal compound semiconductors to be deposited.