Dislocation Density of GaN Grown by Hydride Vapor Phase Epitaxy
- PDF / 193,465 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 98 Downloads / 238 Views
Internet Journal Nitride Semiconductor Research
Dislocation Density of GaN Grown by Hydride Vapor Phase Epitaxy Kyoyeol Lee12 and Keunho Auh2 1Samsung Advanced 2Ceramic
Institute of Technology, Materials Research Institute, Hanyang University,
(Received Saturday, October 14, 2000; accepted Saturday, April 28, 2001)
We have investigated the dislocation of GaN films grown by hydride vapor phase epitaxy (HVPE) on c-plane sapphire substrates using transmission electron microscopy (TEM), etch pit density (EPD) characteristics, and micro photoluminescence (PL). Micro PL mapping is a nondestructive method for observing defect sites as dark spots which reveal the dislocations causing non-radiative recombination centers in the GaN film surface. The dark spots reveal a decrease in threading dislocation sites with increasing the thickness of GaN films. In order to illustrate the correlation between the thickness and the dislocation density of GaN, the micro PL analysis method was used to observe the dislocation densities of a GaN film with a low dislocation density.
1
Introduction
In recent years, GaN has attracted the attention of numerous research groups due to its high potential for optoelectronic and high-power electronic applications. [1] Properties such as wide direct band gaps and high thermal stabilities make nitride semiconductors the superior material for laser diodes and laser emitting diodes in the blue and ultraviolet wavelength regions, as well as for devices operating at high temperature. [2] Epitaxial film quality with low defect density is of great importance for the success of all devices. Consequently, reducing the dislocation density is one of the key issues in obtaining better device performance. A remarkable reduction in the threading dislocation density has been obtained in several efforts by means of growth at high pressure/temperature using the hydride vapor phase epitaxy method (HVPE). [3] [4] [5] [6] Many researches have been carried out to analyze the characteristicss of dislocations in GaN films. Transmission electron microscopy (TEM), despite the extensive and skillful sample preparation it demands, is the general means to observe dislocation densities and structures. [7] Wet-chemical etching is a commonly used technique for surface defect investigation. [8] [9] Youtsey and co-workers demonstrated a photoenhanced electrical chemical (PEC) etching process that produces highly anisotropic “whisker-like” features in n-type GaN films. Luminescent radiators have also been used to estimate the dislocation’s influence on device reliabil-
ity for high current density conditions in III-V and II-VI materials. Rosner et al. showed, by the comparison of atomic force microscopy (AFM) and cathodoliminescence (CL) images, that the dislocation in GaN is a nonradiative recombination center. [10] Nagahama found that the lifetime of the laser diodes (LDs) is strictly dependent on the dislocation densities of GaN substrates as revealed by dark spots in cathodoluminescence (CL) images. [11] We have recently d
Data Loading...
