Lateral diffusion of sources during selective growth of Si-doped GaAs layers by metalorganic vapor phase epitaxy was analyzed. The diffusion lengths of gallium and silicon species were estimated from carrier concentration profiles measured by Raman spectroscopy and thickness profiles. Using the diffusion lengths obtained, it is speculated that the diffusion materials are monomethylgallium and silylarsine. From their identical diffusion lengths, it was determined that there is no difference in diffusion materials between arsine and tertiarybutylarsine.
We studied the effect of threading dislocation scattering on the mobility of a two-dimensional electron gas. To verify our theory, we grew Si-doped AlGaAs/GaAs selectively doped heterostructures with different dislocation densities by changing the number of thermal annealing cycles. The theory agreed well with our experimental results. Previous work on high electron mobility transistors (HEMTs) fabricated on Si indicated that the device characteristics are insensitive to the dislocation density. Our theory states that the room temperature mobility reduction by dislocations with a density below 108 cm−3 does not affect HEMT device performance, which is consistent with empirically known results.
Capacitance of Schottky barrier diodes formed on Si-doped AlxGa1−xAs (x>0.25) decreases as the measuring frequency increases from 1 kHz to 1 MHz at room temperature. As a result of this frequency dependence, apparent donor concentrations become smaller than the true values at a measuring frequency of 1 MHz, which is widely used for derivation of donor concentrations. This frequency dependence is caused because charging and discharging at DX centers does not follow the 1-MHz measuring frequency even at room temperature. This result is important for characterizing n-AlGaAs and for its applications to electronic and optical devices.
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