Properties of Amorphous Gan Grown on Silicon

Abstract

The success of crystalline GaN as an optical and electronic material has motivated an enormous effort to explore all aspects of the material. Little is known and reported about the amorphous phase of this semiconducting wide band gap material. In this paper, we report on the properties of amorphous GaN (a-GaN) grown on p-Si at 443K using electron cyclotron resonance (ECR) plasma-assisted metalorganic chemical vapor deposition (MOCVD). Silicon is a potential alternative to sapphire due to its high quality and readily available as a large diameter and low cost substrates. The film was analyzed by a variety of methods, including scanning electron microscopy (SEM), atomic force microscopy (AFM) and x-ray diffraction (XRD). The current-voltage characteristics of a-GaN/Si heterojunction were measured from room temperature to 363K. Rectification behavior and photovoltaic effect were observed for this anisotype heterojunction. The electrical characteristics of Ni Schottky barriers on a-GaN were also investigated.

Stabilization of amorphous GaN by oxygen

“…Tetrahedrally-bonded materials require more rapid quenching, so that amorphous Si (a-Si) and Ge are formed by deposition from the vapor onto an ambient-temperature substrate, or by ion implantation or bombardment [3]. In the case of the III-V compounds, including GaN [4,5,6,7,8,9,10,11], claims have been made for amorphous-material preparation by the same techniques as are used in Si technology, though these materials have not been studied at the same level as a-Si. We will argue below that in the case of GaN, at least, the truly amorphous form is unstable in stoichiometric material.…”

“…However, it has been suggested that the amorphous form of GaN (a-GaN) might be particularly interesting in this regard, because the relatively strong ionicity of the Ga-N bond would be expected to limit homopolar bonds that might otherwise introduce states in the gap separating the valence and conduction bands [13]. There have been several attempts to form and study thin films of the material, with mixed results as regards both its preparation and electronic and optoelectronic properties [4,5,6,7,8,9,10,11]. Many of the attempts have generated either nanocrystalline or nonstoichiometric material, and it is unclear from a study of the literature that genuinely stoichiometric a-GaN can be formed.…”

Crystallinity Studies of GaN/Si Films Grown by MOCVD at Various Substrate Temperatures Using XRD

“…This could be an indication that the films are a mixed phase of crystalline and amorphous structure or microcrystalline structure. Previous surface morphology studies of this film have revealed the formation of small grains (microcrystallites) [3]. Therefore, the structure of GaN films grown at 600°C can be considered to be in microcrystalline phase.…”

Structural and optical properties of GaN-based nanocrystalline thin films

“…material consists of random-stacked nanocrystals of about 3 nm diameter and will be further considered in this work as stoichiometric GaN. Its structural and optical properties can be adjusted through doping with different elements [3,6,[7][8][9][10][11]. This paper has a focus on the annealing effects on stoichiometric GaN, GaN:O and GaN:Mn.…”