Optical characterization of low temperature grown GaAs by transmission measurements above the band gap

Abstract

Articles you may be interested inTemperature dependence of the refractive index of direct band gap semiconductors near the absorption threshold: Application to GaAs J. Appl. Phys. 80, 4626 (1996); 10.1063/1.363445AlGaAs/GaAs quantum well heterostructures grown by the low temperature LPE technique AIP Conf.Effects of low-temperature-grown GaAs and AlGaAs on the current of a metal-insulator-semiconductor structureWe report on transmission measurements on low temperature grown GaAs and standard GaAs for a spectral range 0.8 -2.8 eV. We measured a drastic reduction of absorption due to annealing over the whole spectral range. The absorption changes depend on the annealing temperature and occur in two individual phases. Additional transmission measurements on samples without antireflection coating confirm our earlier results of an annealing induced refractive index change of ⌬nϷ0.2.

Electronic structure of Ga1−xMnxAs probed by four-wave mixing spectroscopy

“…Smearing of the band edge features with low temperature growth is due to excess arsenic, an effect that has been well studied in LT GaAs. 53,55 Excess arsenic leads to the formation of band tail states associated with local potential fluctuations 55,56 and a deep donor band due to As Ga antisite defects, 28,53 both of which lead to absorption pathways for photon energies below the band gap of HT GaAs. The absorption tail is largest in the LT GaAs sample, as expected because the As Ga mid-gap donor band will be occupied, leading to strong linear absorption from the mid-gap band to the conduction band.…”

Control of the Urbach band tail and interband dephasing time with post-growth annealing in low-temperature-grown GaAs

“…A faster evolution of the defect distribution with higher annealing temperatures 11,30,42 may have contributed to the abruptness in the change of the Urbach energy with annealing temperature observed here, in line with earlier studies of the influence of annealing on the linear absorption spectrum and carrier lifetime in LT-GaAs. 20,42,43 We note that Segschneider et al detected band tail states in an LT-GaAs sample that had been annealed at 600 • C using nonlinear pump probe spectroscopy. 15 The persistence of the band tail in the experiments of Ref.…”

“…This is due primarily to the need to apply nonlinear optical spectroscopy, 15 which enables the band tail states to be isolated from the strong defect-induced absorption that dominates the linear optical response of LT-GaAs. 20,[27][28][29] Here we report the application of four-wave mixing (FWM) spectroscopy to study the influence of annealing on the optical properties of LT-GaAs. The Urbach energy (E U ) was extracted in our experiments from the low-energy tail of the FWM spectrum for a range of annealing temperatures (T a ).…”

“…For instance, the optical promotion of carriers from the mid-gap states to the conduction band results in strong broad-band absorption that obscures the optical band edge. 20 In addition, the band tail states have been shown to reduce the rate of carrier relaxation due to a decreased cross section for trapping into the midgap defect levels, limiting the overall speed of the material response. 15 A good understanding of the defect landscape is therefore essential to optimize the material properties of LT-GaAs and related low-temperature-grown semiconductors for applications.…”

“…11,16,[19][20][21][22][23][24][25] A variety of techniques have been used to study the point defect density as a function of the growth and annealing temperature, including Hall effect, 11 electron paramagnetic resonance, 22 Auger spectroscopy, 16 positron annihilation, 23 and scanning tunneling microscopy. 24,25 These studies have shown that annealing reactions involving defect complexes of As Ga , As i , and V Ga promote the diffusion of As i and the resulting reduction in point defect density through the formation of As precipitates.…”