Transport measurements on a high mobility, ultralow carrier concentration inverted GaAs/AlGaAs heterostructure
✍ Scribed by P.M. Echternach; Kezhong Hu; A. Madhukar; H.M. Bozler
- Publisher
- Elsevier Science
- Year
- 1990
- Tongue
- English
- Weight
- 310 KB
- Volume
- 165-166
- Category
- Article
- ISSN
- 0921-4526
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✦ Synopsis
We have measured the low temperature magnetoresistance and Hall Voltage on an inverted high electron mobility transistor (HEMn structure with ultra low carrier concentration in the dark. We have observed Shubnikov-de Haas oscillations and quantized Hall voltages at very low magnetic fields.
Recently, it has become feasible to study a high mobility two dimensional electron gas (2DEG) with carrier concentration lower than lOll cm• 2 • Such a system is potentially interesting. For example, one estimate for the occurrence of Wigner crystallization requires a 4.2 K mobility of 10 6 cm 2 ;Vs at a concentration of 6xl0 1O cm-2 (1). Commonly, such low carrier concentration 2DEG are realized by illuminating the sample. We report on measurements on a heterostructure that has a 4.2 K mobility of 400,000 cm 2 ;Vs and a carrier concentration of 4 x 10 10 cm• 2 in the dark.
The sample, an inverted HEMT, was grown via molecular beam epitaxy on a semi-insulating GaAs(100) substrate and contains the following layers: an undoped GaAs buffer layer, undoped Alo.25Gaa.7SAs, Si doped (2.5xI0 17 cm• 3 ) Alo Gaa.7SAs (113 A), undoped Alo.25Gaa.7SAs (280 A), undoped GaAs (1360 A). The material was shaped into a Hall bar pattern by etching. The channel lateral dimensions are 120 JIm by 400 JIm.