Selective epitaxy and in-situ etching studies on III-V semiconductor surfaces

Sammanfattning: Semiconductor lasers are widely used in e.g. opticalcommunication networks or data storage and retrieval in CDs orDVDs. As the applications of this type of lasers grow, thedemands on low power consumption, high operating speed, orsmall device size are becoming more important. Theserequirements can be met in certain cases by improvedfabrication and processing techniques. In turn, to be able toimprove these techniques, a good understanding is necessary.This thesis emerged from the need to gain such an understandingwith the view to improve device performance.A Hydride Vapour Phase Epitaxy (HVPE) reactor is used inthis thesis to carry out selective epitaxy and in-situ mesaetching on III-V semiconductor surfaces. Morphologicalevolution during selective epitaxy on non-planar substrates asa function of crystallographic orientation, growth temperatureand V/III ratio is analysed and modelled semi-quantitatively.The analysis is based on the net change of dangling bonds dueto indium addition in a phosphine rich ambient. The evolutionof growth is explained and the repercussion on dopantincorporation is discussed. Knowledge gained from such ananalysis is successfully implemented in the fabrication ofburied heterostructure vertical cavitysurface emitting lasers(VCSELs). The gained knowledge is also applied to the formationof InP templates on FIB (focussed ion beam) patterned GaAssubstrates. These templates can be used for fabricatingmicrostructures and nanostructues or to integrate InP baseddevices with GaAs based onesIn-situ mesa etching is also studied as a function of thepartial pressure of the active gases, (HCl, PH3and InCl), stripe orientation and etchingtemperature. Four major etching mechanisms are proposed whichqualitatively explain the resulting mesa shapes as well asvertical and lateral etching rates. The experimental resultsshow that the depth and the undercut of the mesas can be etchedindependently. Technological importance of combining in-situmesa etching and immediate selective epitaxy of semi-insulatingmaterials is demonstrated through the realisation of buriedheterostructure in-plane lasers (BH-IPL).Keywords:InP, selective epitaxy, regrowth, in-situ mesaetching, buried heterostructures