MOLECULAR-BEAM EPITAXY GROWTH OF INP-BASED LATTICE-MATCHED HIGH-ELECTRON-MOBILITY TRANSISTOR STRUCTURES HAVING A MODIFIED QUANTUM-WELL PROFILE DUE TO ALXGAYIN1-X-YAS (X-8) BUFFER LAYER(Y=0.47)

The quaternary compound, AlxGayIn1-x-yAs (x + y = 0.47-8) lattice-matc hed to InP substrates was realized as a buffer layer in an InP-based l attice-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 Al0.48Gay=0In0.52As to Eg = 0.82 eV for Alx=0Ga0.47I n0.53As by varying Al and Ga mole fraction simultaneously. A self-cons istent analysis revealed, one, that this buffer layer modified the qua ntum-well structure into a triangular-shaped conduction-band profile a nd, two, the disappearance of the quantum-well in valance-band profile . By forming a triangular-shaped conduction-band quantum-well, carrier wave functions drifted farther apart from the heterointerface, leadin g to the reduction of ionized impurity scattering. Disappearance of ho les in a valance band also contributed to the reduction of the hole an d electron recombination scattering. A high electron mobility of 11338 cm(2)/V s with two-dimensional electron gas density of 2.5 x 10(12)/c m(2) was achieved at room temperature. The high electron mobility was believed to have resulted from the modified triangular-shape quantum w ell in which the ionized impurity ion scattering was suppressed. We be lieve that we have achieved the highest room temperature value of elec tron mobility time with two-dimensional electron gas concentration tha t was 2.83 x 10(16)/cm(2) to date for InP-based lattice-matched high e lectron mobility transistors system. PL measurement showed some eviden ces of a high-quality epitaxial growth.