The characterisation of the donors in GaAs epitaxial films by far-infrared photoconductive techniques

Abstract

The high sensitivity of photoconductive techniques is exploited to study the central cell structure on the extrinsic donor spectra of pure n-type epitaxial films of GaAs. Experiments with back-doped samples have enabled the chemical shifts of most of the common donors to be determined with some confidence. The residual contaminants are identified in material from different sources prepared without intentional doping by conventional vapour and liquid phase techniques and by the recently developed 'alkyl' vapour epitaxial process. Each growth process produces a different set of residual contaminants, but samples grown by the same technique in different laboratories have a very similar donor spectrum.

Nonlinear THz Spectroscopy of n-Type GaAs

“…The PL peak corresponds to the 2P→1S transition, the high-energetic components result from recombination between continuum states and ground states. (b) Photocurrent measurement of a GaAs sample with a doping concentration of N d = 8 × 10 12 cm −3 at T=4.2 K taken from reference [32].…”

“…Theoretical works predicted a hydrogen-like absorption spectrum from shallow donors and acceptors [28,29,30], which makes them an interesting model for atomic systems [31]. Experimentally, isolated impurities were studied via photocurrent (PC) [32,33,34] and photoluminescence (PL) [35,36,37] measurements. PC measurements exploit the fact that carriers in the impurity ground state do not contribute to charge transport.…”

“…With increasing doping concentration, the surrounding potential of a donor electron is modified by both the potentials of neighboring impurity atoms and their donor electrons. Figure 5.5 compares the linear absorption spectrum of sample LD (black solid line) to an absorption spectrum measured in a sample having a doping concentration of N d =8×10 12 cm −3 (red dashed line) [32]. The absorption spectrum of sample LD was measured at a lattice temperature of 100 K in a commercial Fourier-transform spectrometer optimized for THz frequencies.…”

“…Linear absorption spectrum of sample LD (black solid line) measured at a lattice temperature of 100 K. It is compared to a photocurrent measurement on a n-type GaAs sample with a doping concentration of N d =8×10 12 cm −3 (red dashed line) taken from[32].…”

Central-cell corrections for Si and S in GaAs in a strong magnetic field

“…Zero-field central-cell corrections have been extensively studied with a view to identifying the different chemical species involved. [8][9][10][11][12][13][14] Compared to this large amount of work on the zero-field case, the magnetic-field dependence of the centralcell correction has been subject to little study. An early report gave the difference in chemical shift for two unidentified donors.…”