Interface-State Measurements of GaAs Schottky Barriers Using Admittance Techniques: Relationship to Barrier Height Instability
Abstract
A recent series of measurements has shown that the barrier height of Schottky diodes on GaAs may change under long term biasing conditions. The aging has been found to occur under reverse bias conditions with a logarithmic dependence on time. This study has been concerned with looking at the interface- state configuration of these diodes using admittance techniques to see if interface-state generation/destruction plays any role in this aging process. Two groups of diodes, Au/W/GaAs and Au/Pt/Ti/GaAs, were studied. Both of these diode types are contained within power MESFET structures. As has been reported elsewhere, the Au/W/GaAs, diodes exhibit pronounced aging effects, while the Au/ Pt/Ti/GaAs diodes show this effect only slightly. Two variations of the admittance technique were tried. The first variation, which looked for conductance variations as a function of frequency, was not successful, presumably due to the relatively large values of conductance already present in these structures making small variations impossible to see. The second variation looked at forward bias capacitance using a specially modified bridge circuit which enabled the large conductance signal to be nulled out. In order to obtain the interface-state densities from the forward bias capacitance data several assumptions had to be made so that existing theory could be applied. The first of these was that the responsible species are donor interface-states which reside in the upper half of the bandgap.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1990
- Accession Number
- ADA225459
Entities
People
- Keith A. Christianson
Organizations
- Calspan