Pyramidal shaped pit formation on InAlAs/Fe-doped InP structures grown by MOCVD

Epitaxial growth of semi-insulating Fe-doped InP (InP:Fe) by metal organic chemical vapor deposition (MOCVD) has been studied for electronic and optical device applications. For the growth of InP-based hetero-FETs such as InAlAs/InGaAs high electron mobility transistors (HEMTs), highly resistive InP:Fe buffer layers between InAlAs carrier confinement layers or InGaAs channel layers and InP substrates are important because MOCVD grown undoped-InP buffer layers often give leakage currents due to conductive paths caused by Si contamination at the buffer layer/substrate interface. We grew InAlAs/InP:Fe structures, and found that large pyramidal pits were formed on the structures with Fe-doping concentrations above 2/spl times/10/sup 17/ cm/sup -3/. To clarify the mechanism of pit formation and suitable growth conditions of InAlAs/InP:Fe structures for buffer layers, we investigated various growth condition dependencies of shape, size and density of the pits.