Growth and characterisation of Indium antimonide and its heterosturctures

Abstract

In conclusion, InSboriented layers have been grown on InSb and GaAs by LPE. While stepcooling yielded good homoepitaxial layers, it was necessary to use the rampcooling technique to grow InSb on GaAs. The narrow rockingcurve width for the (400) reflection in InSb films on GaAs indicates good structural perfection of the grown layer and low dislocation density in the film. However, the surface morphology of the heteroepitaxial films requires considerable improvement. It was also observed that modifications in growth parameters led to the growth of misoriented layers and interesting nucleation morphologies in the heteroepitaxial case. It was further possible to grow ternary InTlSb on GaAs using the same set of growth parameters as for InSb/GaAs. Growth was confirmed by the shift of the bandabsorption edge to longer wavelengths, characteristic of InTlSb.

Switching Studies In conclusion, the first observation of switching at voltages below 1V for aSi:Hbased structures on III-V substrates is reported here. Good rectification and switching characteristics have been observed. A simplistic model has been used to explain the switching phenomenon. The low switching thresholds make the structure very promising because of its TTL compatibility.

BridgmanGrown Crystals In this work, the vertical and horizontal Bridgman techniques have been used to grow single crystals of high purity and large mobility. An extremely useful contribution of this work is the study of the solid-liquid interface position and its influence on crystal quality. The results and their analysis demonstrate that solidification in meltgrowth techniques does not necessarily occur at the congruentmelt temperature. In the case of indium antimonide, significant supercooling is observed. Movement of the solid-liquid interface away from the meltingpoint isotherm in both directions was recorded, and this was shown to lead to incongruent growth. A set of growth parameters promoting congruent growth has been derived, yielding crystals of superior quality. It is generally believed that the vertical Bridgman technique, being containerconstrained, introduces significant inbuilt stress and is therefore less preferred than the horizontal method, where the growing crystal is partially free from the crucible. This is particularly true for InSb. Since both vertical and horizontal techniques were used in the present study, a comparative assessment was possible. It was found that when growth conditions are optimized, the vertical technique can also yield crystals of comparable quality.

LPE Thin Films and Heterostructures Indium antimonide thin films were grown by homoepitaxy using liquidphase epitaxy (LPE). The films showed good surface morphology and complete coverage. Growth of InSb on latticemismatched substrates such as GaAs was also attempted with considerable success. Preliminary studies on ternary alloy InTlSb were conducted. These heterostructures are of substantial technological relevance for infrared detectors. The use of a versatile and costeffective technique such as LPE, compared to MOCVD or MBE, opens opportunities for discrete device fabrication. Additionally, interesting results on nucleation and island morphology of InSb on GaAs were obtained.

PLDGrown InSb on CdTe In recent years, III-V/II-VI mixed heterostructures have attracted significant interest. In this work, oriented singlecrystal films of InSb were grown on CdTe by pulsedlaser deposition (PLD). Although PLD is not traditionally used for semiconductor growth, its fast growth rate and low growth temperature were particularly advantageous for InSb/CdTe. Layers with good surface morphology and abrupt interfaces were obtained. Strategies to avoid interface reactions forming indium telluride were developed. Photoluminescence studies identified the interfacial species as InTe rather than InTe, contrary to some earlier reports.

aSi:H / InSb Device Structures As an example of crystalline/amorphous semiconductor heterostructures, the aSi:H/InSb interface was investigated. Very useful results were obtained. Metal/aSi:H/InSb device structures exhibited switching at very low voltage thresholds. A simple banddiagram model has been used to explain the observed behaviour. Such a device holds considerable technological potential.