Maslar James, Hurst Wilbur, Wang Christine A
National Institute of Standards and Technology, Chemical Science and Technology Laboratory, 100 Bureau Drive, Stop 8360, Gaithersburg, Maryland 20899-8360, USA.
Appl Spectrosc. 2007 Oct;61(10):1093-102. doi: 10.1366/000370207782217789.
The interpretation of Raman spectra of GaSb can be complicated by the presence of a so-called surface space-charge region (SSCR), resulting in an inhomogeneous near-surface Raman scattering environment. To fully interpret Raman spectra, it is important to have an understanding of the SSCR profile relative to the Raman probe depth. However, a priori determination of even the actual SSCR width is not always possible for GaSb under a wide range of doping levels. The primary objective of this report is to provide a convenient reference to aid in the determination of relative contributions to an observed GaSb Raman spectrum of SSCR scattering and bulk scattering for a range of excitation wavelengths, doping levels, and SSCR widths and types. Raman spectra of both n-type and p-type doped GaSb epilayers were obtained using 488 nm, 514.5 nm, 647.1 nm, and 752.55 nm excitation radiation. Both n-type and p-type doped GaSb epilayers were selected for investigation because these layers exhibit the two different SSCR types that are typically encountered with as-grown GaSb and related materials. A range of doping levels were examined for each doping type so as to examine the effects of a varying SSCR width on the observed spectra. A secondary objective of this report is to demonstrate the performance of a spectroscopic system based on 752.55 nm excitation that is sensitive to bulk carrier properties in n-type and p-type doped GaSb epilayers over a wide doping range, unlike visible-wavelength-based optical systems.
GaSb拉曼光谱的解释可能会因所谓的表面空间电荷区(SSCR)的存在而变得复杂,这会导致近表面拉曼散射环境不均匀。为了全面解释拉曼光谱,了解相对于拉曼探测深度的SSCR分布很重要。然而,对于处于广泛掺杂水平的GaSb,即使先验确定实际的SSCR宽度也并非总是可行的。本报告的主要目的是提供一个方便的参考,以帮助确定在一系列激发波长、掺杂水平、SSCR宽度和类型下,SSCR散射和体散射对观察到的GaSb拉曼光谱的相对贡献。使用488 nm、514.5 nm、647.1 nm和752.55 nm激发辐射获得了n型和p型掺杂GaSb外延层的拉曼光谱。选择n型和p型掺杂GaSb外延层进行研究,是因为这些层呈现出在生长态GaSb及相关材料中通常遇到的两种不同类型的SSCR。对每种掺杂类型都检查了一系列掺杂水平,以研究变化的SSCR宽度对观察到的光谱的影响。本报告的第二个目的是展示基于752.55 nm激发的光谱系统的性能,该系统与基于可见光波长的光学系统不同,在很宽的掺杂范围内对n型和p型掺杂GaSb外延层中的体载流子特性敏感。