Improved characteristics for Au∕n-GaSb Schottky contacts through the use of a nonaqueous sulfide-based passivation

Abstract

The influence of nonaqueous sulfide passivation (using Na 2 S in the inert solvent benzene) on Au/ n-GaSb Schottky junction behavior was studied. The junction parameters, Schottky barrier height and ideality factor, were derived and compared with those of as-received GaSb surfaces as well as surfaces treated with aqueous sulfide solutions. The Schottky junction made on as-received GaSb is highly nonideal, while S-based passivation treatment of the GaSb surface before contact formation improves the rectifying behavior, and markedly reduces the reverse current. A benzene-based nonaqueous sulfide treatment results in GaSb surfaces with lower oxide and elemental antimony content than does the aqueous sulfide treatment. The produced Schottky barrier height increases to 0.61 eV and the Au/ n-GaSb contact is close to an ideal Schottky junction. GaSb is an important III-V compound semiconductor for high-speed and optoelectronic devices operating in the infrared and near-infrared region. 1 Due to its small band gap, there is often difficulty in achieving a high-quality metalGaSb Schottky contact with near-ideal current-voltage ͑I -V͒ characteristics. Surface and interface properties are critical in determining metal-semiconductor contact behavior, and the existence of an interfacial layer, or a high density of defect states at the metal and semiconductor interface, can lead to highly nonideal characteristics. Air oxidation of GaSb at room temperature results in a thick overlayer of native oxide and a high concentration of elemental antimony at the oxideGaSb interface. [2][3][4] The presence of elemental Sb at the surface can lead to device degradation. Due to its metallic nature, Sb can increase the surface leakage current and lead to the generation of gap-region surface states, reducing the minority carrier lifetime and limiting device performance. Surface passivation using sulfide-based solutions can effectively remove the native oxide and improve the surface electronic and electrical properties. [5][6][7] Previous studies of the sulfurbased passivation using a ͑NH 4 ͒ 2 S-water solution have shown improved Schottky characteristics with a Au-GaSb barrier of 0.52-0.57 eV being reported. 8,9 The use of an aqueous process however, with and without S passivation, leads to a variety of results in the formation of a Au-GaSb Schottky diode with a wide range of the barrier height values being reported, even exceeding the band-gap energy. 10 Further improvements in the reproducibility and stability of the Au-GaSb diodes require a thorough removal of surface oxides and elemental Sb which entails a nonaqueous environment. Nonaqueous passivation using an inert solvent, such as benzene, as the sulfidization medium results in a GaSb surface with decreased amounts of oxide residue and elemental Sb content compared to that generated by aqueous sulfide treatment. 7 In this work, the impact of a nonaqueous S-based passivation treatment on the Au/ n-GaSb Schottky junction behavior was studied. In particular, a nonaqueous sulfide passivat...

Band offsets determination and interfacial chemical properties of the Al2O3/GaSb system

“…7 As a result of the oxidation process, a layer of elemental Sb is formed at the oxide/GaSb interface, which leads to a high leakage current. 8 To overcome these problems, various surface passivation methods, including wet and dry chemical processes, were proposed in an effort to improve the GaSb interface characteristics. 9,10 However, the growth of surface suboxides which degrades the quality of the surface was detected for all passivation techniques.…”

Optical investigation of GaSb thin films grown on GaAs by metalorganic magnetron sputtering

“…The III-V compound semiconductor gallium antimonide (GaSb) has in recent years attracted much attention as an important material for infrared (IR) optoelectronic and electronic device in the wavelength range 1-5 μm [1][2][3][4][5][6][7][8][9][10][11][12][13]. GaSb has an energy bandgap of 0.70 eV (1.77 μm) at room temperature (RT) and 0.81 eV (1.53 μm) at 4 K [14].…”

Probing deep level centers in GaN epilayers with variable-frequency capacitance-voltage characteristics of Au∕GaN Schottky contacts

“…These are not well understood and are thus being actively investigated. [2][3][4][5][6][7][8] Having a work function of ϳ5.1 eV, gold ͑Au͒ is one of the most used metals in the fabrication of metal-semiconductor Schottky and Ohmic contacts. For Au/ GaN Schottky contacts, several groups have reported their results.…”