Growth Of High Quality GaN Thin Films By MBE On Intermediate-temperature Buffer Layers

Abstract

We report the growth of high quality GaN epitaxial layers by rf-plasma MBE. The unique feature of our growth process is that the GaN epitaxial layers are grown on top of a double layer that consists of an intermediate-temperature buffer layer (ITBL), which is grown at 690°C and a conventional low-temperature buffer layer deposited at 500°C. It is observed that the electron mobility increases steadily with the thickness of the ITBL, which peaks at 377 cm2V−1s−1 for an ITBL thickness of 800 nm. The PL also demonstrated systematic improvements with the thickness of the ITBL. Our analyses of the mobility and the photoluminescence characteristics demonstrate that the utilization of an ITBL in addition to the conventional low-temperature buffer layer leads to the relaxation of residual strain within the material resulting in improvement in the optoelectronic properties of the films. A maximum electron mobility of 430 cm2V−1s−1 can be obtained using this technique and further optimizing the growth conditions for the low-temperature buffer layer.

Gallium Nitride: An Overview of Structural Defects

“…They observed that the dislocation density was reduced by 3 orders of magnitude, from 10 10 cm -2 in the first high temperature GaN to 8×10 7 cm -2 in the second GaN. Apart from that, similar result was also obtained by W. K. Fong (Fong et al, 2000). High quality GaN films were grown by molecular beam epitaxy on intermediate-temperature buffer layers.…”

Fabrication and characterization of indium‐tin‐oxide/GaN visible‐blind UV detectors

“…A novel double buffer layer (DBL) structure consisting of a 20 nm AlN high temperature buffer layer and 800 nm GaN intermediate temperature buffer layer (ITBL) was first deposited on a sapphire substrate. This is followed by the growth of a 1µm thick GaN epitaxial layer at about 740 ºC [10,11]. The ITO films were deposited onto the GaN layers by electron beam evaporation using ITO pellet source with In 2 O 3 and SnO 2 in a ratio of 9:1 by weight.…”

Characterization of low-frequency noise in molecular beam epitaxy-grown GaN epilayers deposited on double buffer layers

“…Details of the PL setup is found in previous reports. 6,7,9 Detailed investigations on the low-frequency noise characteristics were conducted on the samples over a wide range of temperatures. Interdigitated devices were fabricated by sputter deposition of Ti/Al ͑30 nm/70 nm͒ bilayers on samples I, II, and III.…”

“…It was shown that the use of the DBL resulted in substantial improvements in both the optical and electronic properties arising from strain relaxation of the top GaN epitaxial film during the epitaxial growth process. [6][7][8][9] It has also been reported that the growth conditions of the thin buffer layer ͑TBL͒ may affect the quality of the ITBL grown on top, which, in turn, will have significant impact on the quality of the top epitaxial layer. 6,7 In this article, detailed studies were performed to investigate the effect of different DBL systems on the quality of the GaN epilayers.…”

“…[6][7][8][9] It has also been reported that the growth conditions of the thin buffer layer ͑TBL͒ may affect the quality of the ITBL grown on top, which, in turn, will have significant impact on the quality of the top epitaxial layer. 6,7 In this article, detailed studies were performed to investigate the effect of different DBL systems on the quality of the GaN epilayers. Investigations on the electronic and optical characteristics of the films will be presented and, in particular, we will report detailed studies of the low-frequency noise characteristics measured from the materials.…”