Raman Spectroscopy of n-Type and p-Type GaSb with Multiple Excitation Wavelengths

Abstract

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. Hence, 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 relatedThe Lincoln Laboratory portion of this

Raman spectroscopic determination of hole concentration in p-type GaSb

“…Unless otherwise noted, spectra were obtained using 752.55 nm radiation from a krypton ion laser, as described previously. 28 Laser radiation was focused on to the specimen with a cylindrical lens and the corresponding power density at the sample was less than ≈9 W/cm 2 . The power density was kept relatively low so as to minimize the effects on the spectra of laser-induced heating of the sample and minimize the generation of photoexcited carriers.…”

“…[10][11][12][13][14][15][16][17][18][19][20][21][22][23] In contrast, only a few investigations of p-type GaSb have been reported. [24][25][26][27][28] Of these reports, one involves the same epilayers investigated here: zincdoped in the range of 1.92 x 10 17 cm -3 to 6.38 x 10 18 cm -3 , as determined from single magnetic field Hall effect measurements. 28 The focus of Ref.…”

“…[24][25][26][27][28] Of these reports, one involves the same epilayers investigated here: zincdoped in the range of 1.92 x 10 17 cm -3 to 6.38 x 10 18 cm -3 , as determined from single magnetic field Hall effect measurements. 28 The focus of Ref. 28 was on the effects of different scattering excitation wavelengths on the observed GaSb spectra and not specifically bulk coupled mode spectra, although such spectra were shown.…”

“…28 The focus of Ref. 28 was on the effects of different scattering excitation wavelengths on the observed GaSb spectra and not specifically bulk coupled mode spectra, although such spectra were shown. The report by Chen et al 24 involves epilayers that were heavily carbon-doped at levels greater than 10 19 cm -3 , as determined from single magnetic field Hall effect measurements.…”

“…This optical system is more sensitive to bulk GaSb coupled mode scattering than the visible wavelength excitation-based optical systems utilized in previous reports of p-GaSb Raman spectra. 28 A relatively simple model for quantitative determination of hole concentration from the bulk coupled mode spectra was evaluated. A simple spectral model was utilized so as to minimize model parameters and thereby limit errors associated with uncertainty in GaSb material properties.…”