Investigation of segregation phenomenon in III-V semiconductors and ways to limit segregation

The segregation of In during InGaAs growth on GaAs (001) and Sb segregation during InAsSb growth on InAs (001) and (111) were studied. X-ray diffraction (XRD) measurements combined with kinematical simulations were used to quantify the extent of segregation occurring in these structures. It was found that ≈1.4 ML of In segregate to the surface and it gets incorporated into the GaAs layer up to a length of about 2--2.5 nm during normal growth conditions. Similarly, about 0.8 ML of Sb was seen to segregate in the case of InAsSb, and this corresponded to a segregation length of about 1.5 nm into the InAs layer in the (111) case and about 2 nm in the (001) case.;Different techniques were studied to prevent segregation. Bismuth was used as a surfactant in the case of InGaAs growth on GaAs to suppress In segregation. In the case of InAsSb/InAs system, Sb pre-deposition technique was employed to compensate for the lost Sb through segregation. In both cases, sharper interfaces were obtained. Sb pre-disposition led to abrupt InAsSb on InAs interfaces while Bi surfactant led to an overall improvement in the InGaAs/GaAs heterostructure growth. Bismuth mediated growth gave samples which gave stronger photoluminescence (PL) emission. This was attributed to reduced segregation and smoother interfaces.;Further studies were carried out to determine the effects of growth conditions such as substrate temperature, composition, arsenic purging etc. on segregation. The substrate temperature was reduced from the normal 520°C to room temperature in the case of InGaAs/GaAs heterostructures. As the growth temperature decreased, the segregation length came down from 2.5 to 1 nm. A study on AsH3 purge effect was done on InAsSb growth on InAs (001), which showed that the purging helped to reduce the Sb segregation length from 2 to 0.7 nm. This sample also gave ≈3--4 times more intense PL intensity. With increasing composition, the segregation length was seen to increase in both InGaAs/GaAs and InAsSb/InAs systems. This causes the PL intensity to decrease suggesting that increased segregation length can lead to a reduction in PL intensity.