Carrier localization effects in GaAs1−xSbx/GaAs heterostructures

Abstract

We investigated the structural and optical properties of GaAs1−xSbx/GaAs heterostructures grown by molecular beam epitaxy on GaAs (001) substrates for Sb concentration up to 12% by means of high-resolution X-ray diffraction and photoluminescence. The correlation between our structural and optical analysis revealed that compositional fluctuations induced localized states which trap carriers at low temperature. Under low excitation power, the photoluminescence (PL) spectra are composed of two competing peaks in the temperature range of 30–80 K. The lower energy peak is associated with transitions from localized states in the band-tail of the density of states while the higher energy peak corresponds to transitions from free carriers. A model based on a redistribution process of localized excitons was used to reproduce the S-shape behavior of the temperature dependent PL. Reducing the growth temperature from 500 °C to 420 °C suppressed the S-shape behavior of the PL indicating a reduction in compositional variation.

Thickness-Dependent Defect Evolution in GaAs0.92Sb0.08/GaAs Heterostructures

“…The contrast modulations observable in Fig. 2(b) for the same sample are indicative of slight compositional inhomogeneities in the film during growth, also observed by photoluminescence [3]. Substantial interfacial defects were present in thicker GaAs0.92Sb0.08 layers.…”

Lattice‐Optimized GaAsSb/InP Heterojunction Toward Both Efficient Carrier Confinement and Thermal Dissipation

“…[13] Our results are different from the previously reported results, which claimed that the degree of carrier localization state increases as the Sb composition increases. [6,12] The difference is attributed to the relatively high Sb content of the GaAsSb samples used in our investigation.…”

“…[5] However, the alloy fluctuations in GaAsSb always cause localized states, leading to carrier localization effects. [6,7] Such localization effects have been observed in many III-V alloy compounds [8] and dilute III-V nitrides (bismides) [9,10] at low temperatures.…”

“…[6,7] With an increase in temperature, the PL peak energy initially exhibits a redshift (T < 30 K) and then a blueshift at T < 60 K. The observed strong blueshift with increasing temperature reveals a gradual thermal activation of the localized excitons to the delocalized states. [6] Finally, at temperatures higher than %60 K, the carriers become delocalized and the PL peak energy starts to have a second redshift due to the bandgap shrinkage. [17] The relationship between the temperature and PL peak position for different Sb compositions is shown in Figure 2d, where the S-shape behaviors are typical characteristics of carrier localization effects, which originate from potential fluctuations induced by strain or alloy fluctuations.…”

“…However, most investigations have focused on the carrier localization in GaAsSb epilayers grown on GaAs with limited Sb concentrations less than %13%, which indicates that as the Sb composition increases, the degree of the localization state increases as well. [6,12] Quite little work has been done on the carrier localization properties of GaAs 1-x Sb x grown on InP with midcompositions (0.3 < x < 0.6). Very recently, Zhang et al [13] have investigated the effect of thermal annealing on carrier localization in GaAsSb with Sb content %56%.…”