Anodic Oxidation Of GaAs Research Articles

Oxidation Patterning of GaAs by Nanoelectrode Lithography

Nanoelectrode lithography, which transfers patterns from a nanoelectrode to a target via an electrochemical reaction, is employed for patterning GaAs. Gallium oxide and arsenic oxide are produced by the anodic oxidation of GaAs. A-400-nm pitch line and space (L/S) pattern and a closely packed hexagonal pattern with a 500 nm pitch are successfully transferred. For the 400-nm-pitch L/S pattern, a patterned area of 6×8 mm2 is obtained with a reaction time of 30 s. The fabricated pattern can be directly used as an etching mask. Structures with depths of approximately 70 and 10 nm are obtained by wet and dry etchings, respectively. In addition, it is confirmed that multiple patterning is also possible on a GaAs substrate.

Pulsed anodic oxidation of GaAs for impurity-free interdiffusion of GaAs/AlGaAs quantum wells

The use of pulsed anodic oxidation of GaAs for impurity-free quantum well interdiffusion is demonstrated. The GaAs capping layer of a single GaAs/Al 0.3 Ga 0.7 As quantum well structure was oxidized and rapid thermal annealing (RTA) at 900°C for 60 s was carried out to create atomic interdiffusion. X-ray photoelectron spectroscopy was used to study the anodic oxide both before and after RTA. The defects created in oxidized p-GaAs epitaxial layers were also studied using deep-level transient spectroscopy (DLTS). The possible mechanisms that generate excess gallium vacancies, V Ga , during either the anodic oxidation process or RTA to promote interdiffusion of the GaAs/AlGaAs quantum well are discussed.

The anodic oxidation of GaAs in an oxygen plasma generated by a D.C. electrical discharge

The anodic oxidation of GaAs was carried out in an oxygen plasma generated by a d.c. glow discharge. This method is a dry and low temperature process. The thickness of the oxide films is proportional to the oxidation time except during the initial few minutes, and the grown films are glassy and uniform. The concentration ratio of arsenic, gallium and oxygen in the oxide was found to be 1:2–3:4 by Auger electron spectroscopy. The oxide dissolved easily in most commonly used acids and alkalis. It had an electrical resistivity higher than 10 15 Ω cm at 15 V and withstood an electrical stress of 1 × 10 6 V cm -1. The density of states at the oxide-GaAs interface was obtained by measuring the capacitance-voltage characteristics of metal-oxide-semiconductor diodes and was found to be 10 12 eV -1 cm -2 at the minimum. An insulated gate field-effect transistor was fabricated using this oxide, and the electron mobility in the channel was 3750 cm 2 V -1 s -1.

Invited paper. Anodic oxides on GaAs. I. Anodic native oxides on GaAs

The anodic oxidation of GaAs is a technologically simple and a low temperature process enabling the production of reproducible high-quality native oxides on GaAs. The paper describes the influence of the GaAs properties and the best conditions for the anodic behaviour of GaAs. The initial phase of the oxide formation was also investigated in two different electrolytes. The minimum thickness of the native oxide covering the whole surface of GaAs was found to be a function of the anodic current density employed and can be as thin as 11 Å.

GaAs-MOS capacitor with native oxide film anodized in nonaqueous electrolyte

Anodic oxidation of GaAs in a new nonaqueous electrolyte and MOS characteristics are described. The anodic oxide film with specific resistivity of 10 14–10 15 Ω cm and breakdown field strength of 2 × 10 6 V/cm was grown at a rate of 22 Å/V for a current density of 0.5 mA/cm 2 in the electrolyte of a saturated ethylene glycol solution of potassium dichromate. A linear relationship between the oxide thickness and the forming voltage was maintained in spite of nonlinearity between the forming voltage and the anodization time. After a shorter time annealing for about 30 min than in an aqueous electrolyte, the new MOS capacitor shows improved interface properties with a small hysteresis and has a noticeable feature of sensitivity to light, and no hysteresis in the C-V curve was observed under light illumination of higher photon energy than about 1 eV.

Anodic Oxidation of GaAs Using Oxygen Plasma

Anodic oxidation of GaAs using oxygen plasma, produced by high-frequency (420kHz) electrodeless discharge in oxygen with the pressure of about 0.1–0.3 torr, has been carried out. A GaAs chip was located outside the plasma generating region in order to keep its temperature below 300°C. Positive voltage of 10–100 V with respect to the plasma was applied to the chip. The oxidation rate K is proportional to the dc current, and depends on the position and temperature of the chip, and on the oxygen pressure, but neither on the carrier concentration (1016–1018 cm-3) nor on the surface orientation. The oxidation rate is represented by K=4.2×10-4exp [q(-1.5+4.4×10-7Eox)/kT] (cm/s), where the electric field in the oxide Eox is in V/cm. The current efficiency is about 10–50%. The oxide is uniform and glassy, readily dissolved in acids and alkalis and slowly attacked by hot water. No change of oxide thickness by heat treatment is observed up to 500°C. The C-V characteristics of MOS capacitors show the injection-type hysteresis and frequency dispersion in the so-called accumulation region, especially those for n-type substrate.

A new technique for device compatible anodic oxidation of GaAs

A simple and effective new technique has been demonstrated which improves markedly the chemical and electrical properties of heat-treated anodic oxide films on GaAs. This technique should facilitate the use of anodic oxides in innovative GaAs devices.

On the Behaviors of the Cell Voltage during Anodic Oxidation of GaAs under Dark and Illuminated Conditions

On the Behaviors of the Cell Voltage during Anodic Oxidation of GaAs under Dark and Illuminated Conditions

Anodic Oxidation of GaAs in Mixed Solutions of Glycol and Water

A native oxidation of by anodization in mixed solutions of glycol and water (AGW) is described. A detailed comparison between the AGW process and anodization in aqueous solutions (AAS) shows the basic importance of (i) the simultaneous oxide dissolution during growth and (ii) the initial electrochemical active‐passive transition of the anode. The results demonstrate the substantial superiority of the AGW process over various AAS processes. Factors relevant for uniform, stable, and reproducible oxidation are studied which include the effects of illumination, sample edges, and stirring. The dependence of the thickness‐voltage rate constant on the current density is established. The AGW process exhibits a high current efficiency.

Anodic Oxidation of GaAs as a Technique to Evaluate Electrical Carrier Concentration Profiles

An anodic oxidation process of p‐ and n‐type , using a constant current source, is described. Homogeneous and reproducible oxide layers were obtained using N‐methylacetamide adjusted to a pH value of 8.3 by . For chemically polished and etched surfaces, oxide growth was found to be 20.2 Å/V and the amount of consumed in the oxide was 13.4 Å/V. This technique has been successfully applied to differential sheet resistivity and Hall measurements on ion‐implanted semi‐insulating .

Improved method of anodic oxidation of GaAs

A new and better electrolyte for anodic oxidation of GaAs is described. It is an aqueous solution of tartaric or citric acid mixed with glycol and can produce, in an extremely stable manner, native oxide films with remarkably improved dielectric properties.

The Anodic Oxidation of GaAs in Aqueous H 2 O 2 Solution

The characteristics of anodization at constant applied voltage, V, in a concentrated (30%) electrolyte are examined in detail. Uniform oxides, with a refractive index of 1.8 and oxide thickness, t, proportional to V, are grown over the pH range 1–6. The pH can be adjusted by the addition of or to the electrolyte but the presence of other common acids at concentrations of a few parts per million can transform the anodization process into an etching procedure. In 10 min anodizations at of oxide are grown and are consumed on chemically polished surfaces (for ). The resistance of the electrolyte causes significant voltage drops in the electrolyte at all pH values and limits the initial current flow. Most of the oxide is grown during the initial anodization (typically in the first minute) where the current is decreasing rapidly with time and the voltage drop across the oxide is increasing. The oxide is insoluble in the but is soluble in most other acids and bases. Limited MOS measurements yield a dielectric constant of 5.4 and a breakdown field of . The use of the oxide as a mask for chemical etching was demonstrated by forming passive optical waveguides in epitaxial layers.