Evaluation of Heterojunction Interfaces Using Electron Beam Electroreflectance
Abstract
The Phase I study of heterojunction III-V layers using EBER is completed. In the case of single films, the direct band gap of AlxGa 1-x As composition from the entire range x=0 to 1 is detectable. The excitonic energy levels of a wide range of AlGaAs/GaAs single quantum wells. The observed levels have been identified with respect to the simple rectangular barrier model. In HEMT studies, our EBER studies strongly suggest the presence of 2DEG states at the heterojunction interface, as reported by earlier researchers. In addition, direct evidence is found of superlattice buffer layers in HEMTs, which has not been previously reported. Furthermore, The Franz-Keldysh oscillations originating in the heavily doped AlGaAs film is utilized to estimate the built- in electric fields in HEMT samples. Although not yet correlated to the 2DEG density nor carrier mobility to features of EBER spectra, the poor quality HEMT material can be detected. Theses studies have encompassed fundamental investigations of the mechanism of EBER, the presence of excitons in crystals and structured samples. Also measured are the EBER spectra of strained-layer pseudomorphic QW and HEMT structures Additionally, data shows that carrier type can be determined optically from the phase of the EBER features. Keywords: Electroreflectance; Heterojunction; Interface semiconductor; High electron mobility transistor; Field effect transistors.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 18, 1989
- Accession Number
- ADA208072
Entities
People
- Michael H. Herman