Persistent Photoconductivity in a High Mobility two Dimensional Electron Gas in an AlGaN/GaN Heterostructure
- PDF / 66,795 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 5 Downloads / 198 Views
Persistent Photoconductivity in a High Mobility two Dimensional Electron Gas in an AlGaN/GaN Heterostructure S. Elhamri,1 A. Saxler, D. Cull and W. C. Mitchel Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, Ohio 45433-7707 2 2 3 2,3 C.R. Elsass,2 I.P. Smorchkova,3 B. Heying,2 C. Poblenz, P. Fini, S. Keller, P.M. Petroff, 2,3 3 2 S.P. DenBaars, U.K. Mishra, and J.S. Speck College of Engineering, University of California, Santa Barbara, CA 93106 1 Permanent address: Department of Physics, University of Dayton, Dayton, Ohio 45469-2314. 2 Materials Department 3 Electrical and Computer Engineering Department. ABSTRACT Temperature-variable Hall and Shubnikov- de Haas effects have been used to study persistent photoconductivity in an AlGaN/GaN heterojunction. At liquid helium temperatures, the mobility in this structure was close to 55000 cm2/Vs. A blue GaN-based light emitting diode was used to illuminate the sample. This illumination resulted in a persistent photocurrent, which allowed us to vary the carrier density and study the dependence of the mobility on the carrier concentration. Exposing the sample to this light resulted in an increase in the carrier density. For small increases in the density, the mobility also increased. However, unlike in previous reports by other authors, extended illumination resulted in an increase in the density and a decrease in the mobility. The initial increase in the mobility is attributed to increased screening due to the increase in the carrier density, while the decrease in the mobility may be attributed to alloy scattering. INTRODUCTION Gallium Nitride and its alloys are the subject of intense investigation by many researchers worldwide.1 This is due to their potential applications in high temperature and high power electronic devices,2 visible and ultraviolet light emitting devices,3 and solar-blind ultraviolet photodetectors.4 GaN-based devices such as light emitting diodes (LEDs) and laser diodes are already available commercially.5 The GaN/AlGaN heterostructure has attracted special interest due to its potential applications in high mobility transistors operating at high powers and high temperatures.6-8 In this proceeding, we present our investigation of persistent photoconductivity in a twodimensional electron gas (2DEG) that resides at the interface of a very high mobility GaN/AlGaN heterostructure. The goal of this study is to determine the effects of illumination on the electrical characteristics of this structure. Previous studies of persistent photoconductivity, by other researchers, in both bulk GaN9 and GaN/AlGaN heterostructures10 have focused on the kinetics of buildup and decay times rates of the induced photoconductivity. Whereas in our study we took advantage of the persistent nature of the induced photocurrent to investigate the relationship between the carrier density, the mobility and the scattering times in a single sample. Persistent photoconductivity (PPC) studies are important not only because they allow us to stu
Data Loading...
