Some Low Field Transport Properties of LPE grown GaAs and AlAs Mixed Alloys and Saxena's Deep Donor

Abstract

GaAs and AlAs mixed crystals offer the possibilities of their potential applications in various modern optical, electrical and microwave heterostructure devices to realize complete systems performing various operations for both civil and defence operations. For x >~ 0.25, a deep level, known as Saxena's deep donor dominated the electrical characteristics of Ga/sub 1-x/Al/sub x/As crystals and its activation energy increases with x, being 0.170 eV at x = 0.44, the energy of this level below the X minima decreases with x, reaching a value of 0.106 eV at x = 0.78. The results show that the lowest energy indirect minima is L in GaAs lying 0.280 eV above the T-L cross-over composition is x = 0.47. A long lifetime (T < 50 K) photoconductivity effect is also observed, which is associated with the indirect nature of the deep level. An increase in photo-Hall mobility at low temperatures over the dark mobility shows that this level has the properties of an acceptor-like centre. Shallow donor levels are also present in the crystals, but are heavily compensated. The Hall to drift mobility ratio peaks near the direct-indirect minima cross-over composition and has a peak value of ~ 3.8 at x = 0.42.