Effects of GaN passivation with SiO 2 and SiN x studied by photoluminescence and surface potential electric force micros
- PDF / 201,090 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 120 Downloads / 201 Views
0892-FF23-09.1
Effects of GaN passivation with SiO2 and SiNx studied by photoluminescence and surface potential electric force microscopy S. Chevtchenko, M. A. Reshchikov, K. Zhu, Y.-T. Moon, A. A. Baski, and H. Morkoç Electrical Engineering Department and Department of Physics, Virginia Commonwealth University, Richmond, VA 23284, U.S.A. ABSTRACT The influence of passivation with SiO2 and SiNx on optical properties and surface band bending in unintentionally doped GaN has been studied by steady-state photoluminescence (PL) and surface potential electric force microscopy (SP-EFM). For both types of passivation we observed a significant increase of PL intensity in air ambient at room temperature. The measured surface potential was the same for control and passivated samples within the experimental error. The value of the surface band-bending was determined as 1.0±0.2 eV in all cases. We suggest that the strong enhancement of PL is caused by reduction of contribution of the surface states to recombination of photogenerated carriers after passivation. INTRODUCTION Surface and interface properties of III-V semiconductors attracted a great deal of interest in recent years. Most of these semiconductors exhibit a large density of surface states and, as a result, large band bending at the surface. GaN is no exception, and the presence of surface states can significantly degrade the properties of devices based on GaN. The standard approach to overcome the problems caused by uncontrollable surface states is passivation with dielectric films. In order to reduce the density of surface states and thereby to improve the performance of devices, such as Schottky diodes and FET structures, different types of dielectric films are used. Among the most promising candidates for GaN, surface passivations with SiO2 and SiNx dielectrics are superior. There are a number of works where GaN/SiO2 and GaN/SiNx interface properties have been studied by electrical techniques. The effects of passivation with SiO2 and SiNx on the performance of GaN Schottky diodes1,2, GaN MIS structures3,4, and AlGaN/GaN HFET’s5,6,7 are reported in literature. In spite of numerous studies in this area and reported progress in surface passivation and device performance, sufficient information on the physical properties of passivated GaN, other than those obtained by electrical characterization, is lacking. The goal of this work is to study changes of GaN optical properties with different types of passivation and to find a correlation between these changes and reduction of the surface states by creation of protective layer on the GaN surface. For this purpose we studied the steady-state photoluminescence (PL) of SiO2- and SiNx-passivated GaN layers and compared it with that of an unpassivated sample. We also employed the surface potential electric force microscopy (SPEFM) for surface potential measurements in order to detect any changes in the near-surface band bending. EXPERIMENTAL DETAILS An unintentionally doped GaN film used in this study was grown on c-plane sa
Data Loading...
