FLAT-BAND CURRENT-VOLTAGE-TEMPERATURE METHOD FOR BAND-DISCONTINUITY DETERMINATION AND ITS APPLICATION TO STRAINED INXGA1-XAS/IN0.52AL0.48AS HETEROSTRUCTURES

A method that combines capacitance-voltage and current-voltage-temperature measurements of a n+-i-n- (or p+-i-p-) heterobarrier structure for reliable determination of the band discontinuity is described. Experimental and analytical procedures for the extraction of the Fermi energies in the doped layers, the location of the flat band condition, and the determination of the barrier height at flat band are given. The effects of nonparabolicity and strain are also considered. Some potential sources of errors encountered in the conventional procedure that is based on the barrier height at zero bias are avoided in this flat band method. The application of this method and other experimental considerations are illustrated by using the strained InxGa1-xAs/In0.52Al0.48As heterointerface as a specific example. The results show that the conduction-band offset ratio, Q(c), is nearly constant at 0.71 for x less-than-or-equal-to 0.54 but appears to change quite abruptly to a fairly constant value of 0.82 for x greater-than-or-equal-to 0.58.