XPS and electric analysis of the GaAs(100) nitridation

p. 405 - 409

Gallium nitride is the most promising III-V semiconductor, in many applications. Due to its large direct band gap (3.4 eV), GaN can be dedicated as well to optoelectronics devices, e.g. blue lasers and photo-detectors as to the realisation of transistors operating in high-frequency and high-temperature regimes. Therefore, the technology of GaN films on standard substrates, GaAs, attracts special attention. In this paper, nitridation process of GaAs (100) substrates was studied in-situ using x-ray photoelectron spectroscopy (XPS) and ex-situ by means of electrical methods (I-V and C-V) in order to determine chemical, electrical and electronic properties of the elaborated GaN/GaAs interfaces. At first, native oxides were removed from the n-GaAs (100) surface by an argon ion bombardment. Next, a thin film of GaN was obtained by means of the nitridation on the GaAs substrate in an ultrahigh vacuum system using a radio-frequency plasma source (13.56 MHz), which allows nitridation at low pressures (10^-4 Pa). The Schottky diode (Hg on the fabricated GaN/GaAs structures) was characterised by I-V and C-V analysis. The saturation current I_s, the mean ideality factor n, the barrier height F_BN, and the serial resistance R_s are determined from the I-V measurements. The C-V curves were controlled by the interfacial state density N_SS(E) and by the deep donor levels in the semiconductor bulk. Correlation among chemical, electronic and electrical properties of the GaN/GaAs interface was discussed.