Subthreshold I-V Characteristics of AlGaAs/GaAs MODFETs: The Role of Unintentional Acceptors
Abstract
A strong inversion, depletion layer model of threshold has been extended to describe subthreshold I-V characteristics in MODFETs (modulation doped field-effect transistors). The results of this calculation yield the MODFET equivalent of the MOSFET (metal-oxide semiconductor field-effect transistor) charge sheet subthreshold model. For typical molecular beam epitaxy (MBE) grown structure, the subthreshold current may differ by two-orders of magnitude for a given gate voltage V sub g and drain-to-source voltage V sub ds as the acceptor doping varies from 1 to 100 x 10 to the 13th power. For these acceptor doping densities, the gate voltage, for a given drain-to-source voltage, needed to maintain a constant subthreshold current, varies by only about 0.1 V. If the acceptor density is increased to 10 to the 17th power/cc, a large increase (approx. 0.8 V) in the gate voltage is required to maintain a constant subthreshold current. These changes in subthreshold current with acceptor concentration in the bulk GaAs are significant and need to be included in an accurate MODFET model.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 19, 1990
- Accession Number
- ADA230110
Entities
People
- Richard J. Krantz
- Walter L. Bloss
Organizations
- The Aerospace Corporation