Electrical Properties of InAlAs/InAs_(x)P_(1-x)/InP Composite-Channel Modulation-Doped Structures Grown by Solid Source Molecular Beam Epitaxy

摘要

We report on the electrical characteristics of the two-dimensional electron gas (2DEG) formed in an InAlAs/InAs_(x)P_(1-x)/InP pseudomorphic composite-channel modulation-doped (MD) structure grown by solid source (arsenic and phosphorus) molecular beam epitaxy (SSMBE). The As composition, x, of strained InAs_(x)P_(1-x) was determined by x-ray diffraction analysis of InP/InAs_(x)P_(1-x)/InP multi-quantum wells (MQWs) with compositions of x=0.14 to x=0.72. As the As composition increases, the room temperature sheet resistance of InAlAs/InAs_(x)P_(1-x)/InP composite-channel MD structures grown over a range of As compositions decreased from 510 to 250 Ω/cm~(2), resulting from the greater 2DEG confinement and lower electron effective mass in the InAs_(x)P_(1-x) channel as x increases. The influence of growth conditions and epitaxiallayer layer designs on the 2DEG mobility and concentration were investigated using 300 K and 77 K Hall measurements. As the exposure time of the As_(4) flux on the growth front of InAs_(x)P_(1-x) increased during growth interruptions, the 2DEG mobility, in particular the 77 K mobility, was considerably degraded due to increased roughness at the InAlAs/InAs_(x)P_(1-x) interface. For the InAlAs/InAs_(0.6)P_(0.4)/InP composite-channel MD structure with a spacer thickness of 8 nm, the room temperature 2DEG mobility and density were 7200 cm~(2)/Vs and 2.5×10~(12) cm~(-2), respectively. These results show the great potential of the InAlAs/InAs_(x)P_(1-x)/InP pseudomorphic composite-channel MD heterostructure for high frequency, power device applications.