Epitaxy, analysis and application of semi-insulating III-V materials

Abstract: Semi-insulating (SI) III-V materials can provide electricalisolation for integration and capacitance minimisation for highspeed operation. Compared to the polyimides, these can offerbetter thermal conduction. Ever since the fabrication of thefirst SI III-V materials, transition metals have been utilisedas deep impurities to impart SI properties. Despite the longevolution of certain SI materials, several material propertiesare not entirely established, particularly when 3d-transitionmetals are used as deep impurities. Among all the SI III-Vmaterials, InP:Fe is widely employed in research laboratoriesand industrial production, although it suffers from diffusionof Fe and deficient hole blocking characteristics. Theobjective of this thesis is to gain more insight into materialproperties of SI materials in general and InP:Fe in particularand to exploit them in device fabrication. Attempts have beenmade to grow Ru doped InP using low-pressure hydride vapourphase epitaxy (LP-HVPE). The superior thermal stability andhole blocking capacity of Ru with respect to Fe motivates theinvestigation of InP:Ru. Superior regrowth capability ofLP-HVPE with respect to other techniques motivates its use. Itwas found that InP:Ru was close to the SI behaviour probablybecause of insufficient activation of Ru. To overcome theproblem of low activation, codoped InP:Ru,Fe was grown andfound to yield excellent current blocking behaviour under bothelectron and hole current injection. The codoped structure isalso superior to InP:Fe as regards Fe/Zn interdiffusion.A very direct method, time-resolved photoluminescence hasbeen used to study carrier trapping, which enabled theextraction of capture cross sections of Fe in InP:Fe andGaInP:Fe. The dependence of carrier trapping times on Feconcentration is found to be in very good agreement withresistivity measurements.Modelling of carrier injection in n/SI/n and p/SI/pconfigurations has been carried out. Our modelling indicatesthat deep acceptor concentration and its energy level have adefinite influence on the resistivity of n/SI/n and p/SI/pstructures, in agreement with the observed experimental resultson InP:Fe, InP:Ru and InP:Ru,Fe. Simulated results for InPcodoped with Fe and Ti are also in agreement with the publishedresults available in the literature.To demonstrate the application of SI-InP, buriedheterostructure lasers with good performance have been realisedusing HVPE regrowth of InP:Fe.Keywords: InP, GaInP, semi-insulating materials, irondoping, ruthenium doping, HVPE, diffusion, deep levels, capturecross sections, resistivity analysis, buried heterostructurelaser