Growth of indium phosphide based materials and heterostructures using metalorganic vapor phase epitaxy for high frequency device applications.

Abstract

InP based compound semiconductor materials were grown and characterized using low pressure metalorganic vapor phase epitaxy (LP-MOVPE) for high frequency device applications. In order to provide fully automated, error-free growth environment, a new type of MOVPE growth control software was developed. The impact of growth conditions on the crystalline quality, electrical and optical characteristics of InP, InGaAs and InAlAs layers was investigated. For the growth of InAlAs, deep level characteristics were also addressed. The origin of residual carriers in InAlAs could be explained by deep and shallow donors at low and high growth temperatures, respectively. $\rm In\sb{x}Al\sb{1-x}$As/InGaAs heteroepitaxial diodes have been designed, fabricated and characterized for terahertz multiplier and mixer applications. A qualitative model was proposed to explain the forward conduction mechanisms under different forward bias conditions. A cutoff frequency as high as 2.6THz has been demonstrated experimentally using this diode design. Iron doping of InAlAs layers was explored with the purpose of improving the electrical properties of this material. Time-resolved photoreflectance and temperature dependent low frequency noise measurements techniques were used for characterization and confirmed deep trap formation with activation energy of $\sim$0.77 eV. Impact of iron doping on device characteristics of InAlAs Schottky diodes and InAlAs/InGaAs HEMTs were also investigated and showed that an extremely high diode breakdown voltage of $\sim$90 V could be obtained with properly doped materials. The growth of heavily carbon doped p-InGaAs ($\sim6.5\times10\sp{19}\rm\ cm\sp{-3}$) lattice-matched to InP was explored using CCl$\sb4$ and CBr$\sb4$. Post-growth isothermal and isochronal annealing experiments were performed and a quantitative analysis of carrier activation was proposed based on Hall and SIMS measurements. Reduced self compensation by carbon displacement from indium to arsenic site, as well as, reduced hydrogen passivation were suggested as possible mechanisms responsible for carrier activation upon thermal annealing. MOVPE growth was optimized for high performance InAlAs/InGaAs high electron mobility transistors (HEMTs) and InP/InGaAs heterojunction bipolar transistors (HBTs). High pressure thermal cleaning process was developed to eliminate the highly conductive spike situated at the buffer/substrate interface which contributes to parasitic leakage current. 1$\mu$m gate length InAlAs/InGaAs HEMTs were fabricated using this material and showed high extrinsic transconductance of 400 $\sim$ 550 mS/mm and state of the art microwave characteristics with $f\sb{t}$ of 60 GHz and $f\sb{max}$ of 120 GHz. Fabricated InP/InGaAs HBTs showed $f\sb{t}$ of 95 GHz with open base breakdown voltage value as high as 8 V.