N-type and p-type GaSb metal-oxide-semiconductor capacitors (MOSCAPs) with atomic-layer-deposited (ALD) and plasma-enhanced-ALD (PEALD) Al2O3 dielectrics are studied to identify the optimum surface preparation and oxide deposition conditions for a high quality oxide-semiconductor interface. The ALD Al2O3/GaSb MOSCAPs exhibit strongly pinned C-V characteristics with high interface state density (Dit) whereas the PEALD Al2O3/GaSb MOSCAPs show unpinned C-V characteristics (low Dit). The reduction in Sb2O3 to metallic Sb is suppressed for the PEALD samples due to lower process temperature, identified by x-ray photoelectron spectroscopy analysis. Absence of elemental Sb is attributed to unpinning of Fermi level at the PEALD Al2O3/GaSb interface.

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Fermi level unpinning of GaSb (100) using plasma enhanced atomic layer deposition of Al2O3

While there have been many demonstrations on n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) in III-V semiconductors showing excellent electron mobility and high drive currents, hole mobility in III-V p-channel MOSFETs (pMOSFETs) has traditionally lagged in comparison to silicon. GaSb is an attractive candidate for high-performance III-V pMOSFETs due to its high bulk hole mobility. We fabricate and study GaSb pMOSFETs with an atomic layer deposition Al2O3 gate dielectric and a self-aligned source/drain formed by ion implantation. The band offsets of Al2O3 on GaSb were measured using synchrotron radiation photoemission spectroscopy. The use of a forming gas anneal to passivate the dangling bonds in the bulk of the dielectric was demonstrated. The density of interface states Dit was measured across the GaSb band gap using conductance measurements, and a midband-gap Dit of 3 × 1011/cm2 eV was achieved. This enabled pMOSFETs with a peak hole mobility value of 290 cm2/Vs.

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Optimization of the $\hbox{Al}_{2}\hbox{O}_{3}/ \hbox{GaSb}$ Interface and a High-Mobility GaSb pMOSFET

InAs/(In,Ga)Sb Strained Layer Superlattices (SLSs) have made significant progress since they were first proposed as an infrared (IR) sensing material more than three decades ago. The basic material properties of SLS provide a prospective benefit in the realization of IR imagers with suppressed interband tunneling and Auger recombination processes, as well as high quantum efficiency and responsivity. With scaling of single pixel dimensions, the performance of focal plane arrays is strongly dependent on surface effects due to the large pixels’ surface/volume ratio. This article discusses the cause of surface leakage currents and various approaches of their reduction including dielectric passivation, passivation with organic materials (polyimide or various photoresists), passivation by overgrowth of wider bandgap material, and chalcogenide passivation. Performance of SLS detectors passivated by different techniques and operating in various regions of infrared spectrum has been compared.

Passivation techniques for InAs/GaSb strained layer superlattice detectors

We report a nonaqueous passivation regime consisting of Na2S/benzene/15-crown-5/oxidant. The use of a nonpolar, aprotic organic medium required the addition of a specific chelating agent (15-crown-5) to solubilize sodium sulfide, and organic oxidizing agents (anthraquinone, benzophenone, etc.) to act as electron acceptors. The surface optical and chemical properties of GaSb surfaces after aqueous and nonaqueous sulfide treatments were compared. Nonaqueous passivation resulted in higher photoluminescence (PL) intensity, lower oxide content, and a less amount of elemental Sb than aqueous passivation. The PL intensity from passivated surfaces was correlated with the standard reduction potentials of electron acceptors.

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A comparative study of GaSb (100) surface passivation by aqueous and nonaqueous solutions

Progress and continuing challenges in GaSb-based III-V alloys and heterostructures grown by organometallic vapor-phase epitaxy

The surface preparation of GaSb(100), based on HCl solutions, was studied by x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The chemical and structural analysis by XPS and AFM indicates that the GaSb surface treated by HCl followed by a 2-propanol rinse leads to a 1 to 2 nm oxide layer on the surface. The resulting smooth surface is slightly antimony rich. Surfaces rinsed in deionized water, after HCl-based etching, possess a thicker overlayer, which is depleted of antimony. The surface morphology becomes rough rapidly upon reexposure to air after the HCl/H2O treatment. Other etching processes, including a tartaric acid based etchant, were investigated. Tartaric acid-based etches yield a highly nonstoichiometric surface along with an inhomogeneous etching morphology. The rates of desorption of surface oxides were determined by XPS analysis under ultrahigh vacuum conditions and the typical temperatures of desorption for the constituent chemical component comprising the surface la...

B. Hawkins

Papers

Chemical and structural characterization of GaSb(100) surfaces treated by HCl-based solutions and annealed in vacuum