Infrared studies of hole-plasmon excitations in heavily-doped p-type MBE-grown GaAs:C
| Autor: | R. Zallen, K. L. Bacher, W. Songprakob, W. K. Liu |
|---|---|
| Rok vydání: | 2000 |
| Předmět: | |
| Zdroj: | Physical Review B. 62:4501-4510 |
| ISSN: | 1095-3795 0163-1829 |
| DOI: | 10.1103/physrevb.62.4501 |
| Popis: | Infrared reflectivity measurements ~200–5000 cm) and transmittance measurements ~500–5000 cm) have been carried out on heavily-doped GaAs:C films grown by molecular-beam epitaxy. With increasing carbon concentration, a broad reflectivity minimum develops in the 1000–3000 cm region and the onephonon band near 270 cm rides on a progressively increasing high-reflectivity background. An effectiveplasmon/one-phonon dielectric function with only two free parameters ~plasma frequency vp and damping constant g) gives a good description of the main features of both the reflectivity and transmittance spectra. The dependence of vp 2 on hole concentration p is linear; at p51.4310 cm, vp is 2150 cm . At each doping, the damping constant g is large and corresponds to an infrared hole mobility that is about half the Hall mobility. Secondary-ion mass spectroscopy and localized-vibrational-mode measurements indicate that the Hall-derived p is close to the carbon concentration and that the Hall factor is close to unity, so that the Hall mobility provides a good estimate of actual dc mobility. The observed dichotomy between the dc and infrared mobilities is real, not a statistical-averaging artifact. The explanation of the small infrared mobility resides in the influence of intervalence-band absorption on the effective-plasmon damping, which operationally determines that mobility. This is revealed by a comparison of the infrared absorption results to Braunstein’s low-p p-GaAs spectra and to a k"p calculation extending Kane’s theory to our high dopings. For n-GaAs, which lacks infrared interband absorption, the dc and infrared mobilities do not differ. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|