THE CHARACTERISTICS OF INTIMATE AU-INYAL1-Y SCHOTTKY DIODES - A MISMATCH DEPENDENCE STUDY

The electrical properties of intimate Au-InyAl1-yAs(100) Schottky diod es were studied as a function of InyAl1-yAs alloy composition over a r ange (0.49 < y < 0.55), close to die lattice match (y = 0.52) with the InP(100) substrate. Highly ideal diodes exhibiting the highest report ed Schottky barriers (0.82 eV), measured by the current-voltage (I-V) technique, were obtained on the InyAl1-yAs epilayers most closely latt ice matched to InP. Diodes formed on more mismatched InyAl1-yAs epilay ers were progressively less ideal and exhibited lower barrier heights. The origins of this departure from ideality were investigated by low temperature I-V measurements, indicating that tunnelling via structura l defects in the depletion region may be of greater significance in th e samples with greater mismatch. Furthermore, observations by transmis sion electron microscopy of InyAl1-yAs layers formed under similar con ditions revealed the presence of mismatch dependent, quasi-periodic fl uctuations of alloy composition across the semiconductor surface. Usin g double-crystal X-ray diffraction, the amplitude of compositional mod ulation and the corresponding spatial fluctuations of the band gap wer e estimated, indicating that this may be a possible mechanism by which the effective barrier height is lowered as the InyAl1-yAs/InP mismatc h is increased.