Molecular beam epitaxy growth of InP-based lattice-matched high electron mobility transistor structures having a modified quantum-well profile due to Al xGa yIn 1 − x − yAs( x + y = 0.47−8) buffer layer

Abstract

The quaternary compound, Al x Ga y In 1 − x − y As ( x + y = 0.47−8) lattice-matched to InP substrates was realized as a buffer layer in an InP-based lattice-matched high electron mobility transistors. The band gap energy of this quaternary compound buffer layer was linearly decreased from E g = 1.54 eV for Al 0.48Ga y=0 In 0.52As to E g = 0.82 eV for Al x=0 Ga 0.47In 0.53As by varying Al and Ga mole fraction simultaneously. A self-consistent analysis revealed, one, that this buffer layer modified the quantum-well structure into a triangular-shaped conduction-band profile and, two, the disappearance of the quantum-well in valance-band profile. By forming a triangular-shaped conduction-band quantumwell, carrier wave functions drifted farther apart from the heterointerface, leading to the reduction of ionized impurity scattering. Disappearance of holes in a valance band also contributed to the reduction of the hole and electron recombination scattering. A high electron mobility of 11 338 cm 2/V s with two-dimensional electron gas density of 2.5 × 10 12/cm 2 was achieved at room temperature. The high electron mobility was believed to have resulted from the modified triangular-shape quantum well in which the ionized impurity ion scattering was suppressed. We believe that we have achieved the highest room temperature value of electron mobility time with two-dimensional electron gas concentration that was 2.83 × 10 16/cm 2 to date for InP-based lattice-matched high electron mobility transistors system. PL measurement showed some evidences of a high-quality epitaxial growth.