Semi-Insulating Indium Phosphide Grown with a Carbon Tetrachloride Doping Source.

Epitaxial layers of semi-insulating (SI) InP are useful for a number of optoelectronic device applications. These layers are utilized for current confinement in buried heterostructure lasers, and they have found an application as a Schottky -barrier-enhancement layer in In_ {0.53}Ga_{0.47}As-based devices such as metal-semiconductor-metal photodetectors. They can also be used for device isolation in optoelectronic integrated circuits. The common Fe-doping technique for growing epitaxial semi-insulating InP has serious reliability problems, however, because of the high diffusion coefficient of Fe. This thesis will describe epitaxial layers of SI InP by grown low-pressure MOCVD at substrate temperatures below 500^circC, using a CCl _4 doping source. Based upon experimental data, a mechanism for the electrical properties of the material is proposed. The use of CCl_4 -doped InP as a Schottky-barrier enhancement layer on n-type In_{0.53}Ga _{0.47}As is demonstrated. The resistivity of CCl_4 -doped InP is found to be a function of its growth conditions, especially the substrate temperature and flow rate of diluted CCl_4, and can exceed 10 ^{12} Omega cm. The high resistivity is maintained after annealing. Secondary ion mass spectrometry (SIMS) analysis of the CCl _4-doped InP indicates that high concentrations of carbon, hydrogen, and chlorine are incorporated in the InP layers, and that the incorporation varies with the growth conditions. The growth rate of the InP is reduced by the presence of CCl_4 in the reactor, and the reduced growth rate is attributed to Cl preferentially etching In from the growth surface. Several mechanisms for the electrical properties of CCl _4-doped InP are suggested by this evidence: hydrogen passivation of shallow impurities, incorporation of a Cl- or C-related deep acceptor, and incorporation of a native defect-related deep acceptor. The growth conditions of the CCl_4-doped InP particularly encourage incorporation of the V_ {In} (indium vacancy) native defect, which has been predicted to act as a multiply-charged deep acceptor in InP. The use of CCl_4-doped InP as a Schottky-barrier enhancement layer on n-type In _{0.53}Ga_{0.47 }As is demonstrated. The effects of the thickness and growth conditions of the CCl_4 -doped InP layer on the ideality factor, reverse-bias leakage current, and breakdown voltage of the Schottky diodes are investigated. State-of-the-art results are achieved in all of these figures of merit using this barrier enhancement layer, which, additionally, is expected to have superior reliability characteristics. Forward-bias ideality factors in these diodes are as low as 1.12. The reverse-bias ideality factor is 1.03, and is not affected by the thickness or growth temperature of the CCl_4 -doped InP. Reverse leakage current densities as low as 6.85 times 10^{-5} A/cm^2 are attained, with a barrier height of 0.645 eV.