Solid solution strengthening in GaSb/GaAs: A mode to reduce the TD density through Be-doping

Abstract

The need for a low bandgap semiconductor on a GaAs substrate for thermophotovoltaic applications has motivated research on GaSb alloys, in particular, the control of plastic relaxation of its active layer. Although interfacial misfit arrays offer a possibility of growing strain-free GaSb-based devices on GaAs substrates, a high density of threading dislocations is normally observed. Here, we present the effects of the combined influence of Be dopants and low growth temperature on the threading dislocation density observed by Transmission Electron Microscopy. The Be-related hardening mechanism, occurring at island coalescence, is shown to prevent dislocations to glide and hence reduce the threading dislocation density in these structures. The threading density in the doped GaSb layers reaches the values of seven times less than those observed in undoped samples, which confirms the proposed Be-related hardening mechanism.

Thin Ge buffer layer on silicon for integration of III-V on silicon

“…Use of dopants in the growth of buffer layer layers have been shown to reduce the number of threading dislocations and improve crystal quality [25,26]. Therefore, the last part of this study investigated the impact of dopants on roughness of the samples and TDD.…”

Optical properties of beryllium-doped GaSb epilayers grown on GaAs substrate

“…When Be dopants are introduced in the GaSb sublattice, the density of threading dislocation prorogated into the top GaSb layer from the lattice mismatched GaSb/GaAs interface is reduced due to the Be-related defect "pinning" mechanism , which has been evidenced by high-resolution transmission electron microscopy in Ref. [12]. To further study the effect of Be dopants on the optical quality of the GaSb layers, four representative PL spectra measured from the two samples are plotted in Fig.…”

“…Nominally undoped and intentionally doped GaSb layers with Be (hereafter referred to as "GaSb:Be") were grown on GaAs (001) substrates by molecular beam epitaxy (MBE). Details of the samples growth procedures have been reported elsewhere [12]. The schematic layout of the sample structure is shown in Table 1.…”

“…For instance, improvements in surface morphology and transport properties by beryllium (Be) doping were reported in an InAlAs-based high-electron-mobility transistor grown on GaAs [11]. Moreover, Gutiérrez et al [12] have studied the joint influences of low growth temperature and Be doping on the behaviors of threading dislocation in GaSb layer grown on GaAs substrate. They observed a seven times reduction in the density of threading dislocations in the Be-doped GaSb layer, which was explained by the effective "pinning" of the dislocations by the Be dopants, i.e., the Be-related hardening mechanism.…”

2.5-µm InGaAs photodiodes grown on GaAs substrates by interfacial misfit array technique

“…The IMF transition layer is thicker than previous reports as a result of the solid solution hardening of the GaSb alloy. In other words, with a high doping concentration at this layer, the glide of the misfit dislocations towards the interface is suppressed [10]. The TDs originating from this IMF are mainly confined in the three bottom buffer layers, GaSb, InAs and InAlAs, as shown in Figure 2 X-ray diffraction has been used to assess the quality of the grown materials.…”