Extremely High Mobility of Two-Dimensional Electron Gas in Selectively Doped GaAs/N-AlGaAs Heterojunction Structures Grown by MBE

Abstract

Selectively Si-doped GaAs/N-AlGaAs heterojunction structures have been grown by MBE. Two-dimensional electron gas accumulating at the interface of the heterojunction showed mobilities as high as 69,000 cm2/Vs at 77 K and 100,000 cm2/Vs at 4.2 K, with a sheet electron concentration of 5.5×1011 cm-2, which are higher than any reported so far. An enhancementmode high electron mobility transistor (E-HEMT), which was first fabricated from the heterojunction material, showed a field effect mobility of 49,300 cm2/Vs at 77 K, suggesting that this heterojunction material has potential for application to low-power, high-speed integrated circuits.

Two-dimensional electron gas at the metastable twisted interfaces of CdTe/PbTe (111) single heterojunctions

“…The CdTe/PbTe (111) SHJ bears the similar structural simplicity as well as the performance of AlN/GaN SHJs that also support a 2DEG with high electron mobility up to ∼5000 cm 2 /V s and a sheet density ∼3 × 10 13 cm −2 at 77 K. 12 Compared to those 2DEG structures based on modulation doping, the GaAs/AlGaAs system has been shown to offer higher mobility, for instance ∼69 000 cm 2 /V s at 77 K, but the sheet density is typically lower (∼5.5 × 10 11 cm −2 ); 38 the SiGe/Si has achieved somewhat higher mobility of 9000 cm 2 /V s but a lower density of 1.0 × 10 12 cm −2 at 77 K; 39 the ZnCdSe/ZnSe system has achieved a comparable mobility of 7900 cm 2 /V s at 4.2 K but the carrier density (5 × 10 11 cm −2 ) is nearly two orders in magnitude lower than our structure. 9 Apparently, the achievable 2DEG carrier density in the QWs with the modulation doping approach tends to be lower than that at the interface of a polarized SHJ such as the previously reported AlN/GaN, 12 and the CdTe/PbTe (111) of this work.…”

Localized two-dimensional electron gas formation by focused Si ion beam implantation into GaAs/AlGaAs heterostructures

“…As can be seen in this figure, the oscillations were very weak compared to those observed in usual modulation-doped hetcrostructures. 8 The 2DEG concentration deduced from the oscillation frequency plotted against 1/ B was 7 X 1011 em ... 2 while the electron concentration determined by Hall measurement was 2 X 10 12 cm 2. This implies that not only a 2DEG but also a 3DEG was formed in the GaAs channel layer, consistent with the positive magneto resistance due to the 3DEG mentioned above.…”

Increased mobility anisotropy in selectively doped AlxGa1−xAs/GaAs heterostructures with high electron densities

“…Those high electron mobilities are achieved by employing thick spacer layers, resulting in moderate electron densities around 2ϫ10 11 cm Ϫ2 . In heterostructures with thinner spacer layers higher electron densities up to almost 1ϫ10 12 cm Ϫ2 can be realized [4][5][6][7][8][9][10][11] which is desirable for some applications, e.g., high electron mobility transistors. For those high electron densities, population of the second subband might occur.…”

“…For those high electron densities, population of the second subband might occur. [4][5][6][7][8] The mobility determining scattering mechanisms that have to be taken into account in connection with selectively doped heterostructures are remote impurity scattering, background impurity scattering, and interface roughness scattering. 12,13 Varying the electron density in a given heterostructure, either by applying a gate voltage or, more simply, by stepwise illumination with band gap radiation exploiting the persistent photoeffect, is an established method for distinguishing among different scattering mechanisms: 12,13 For remote and background impurity scattering the mobility increases with increasing electron density, whereas it should decrease for pure interface roughness scattering.…”