Ultrahigh mobility two-dimensional electron gas in AlxGa1−xAs/GaAs heterostructures by organometallic vapor phase epitaxy

Abstract

Ultrahigh mobility AlxGa1−xAs/GaAs two-dimensional electron gas (2DEG) structures were grown by conventional low-pressure organometallic vapor phase epitaxy (LP-OMVPE). We achieved maximum mobilities of 766 000 cm2/V s at 2.2 K and 171 000 cm2/V s at 77 K after exposure to light (to our knowledge, the highest ever by OMVPE growth), with a sheet carrier density of 4.9×1011/cm2. The high-mobility structures were obtained by either growing an AlGaAs-related buffer underneath the 2DEG structure or preconditioning of the reactor with an undoped AlGaAs run. The dark mobilities of samples grown with the preconditioning procedures and without the AlGaAs-related buffer are much higher than those with the buffer.

2×106 cm2/V s electron mobility by metalorganic chemical vapor deposition with tertiarybutylarsine

“…The mobility of the TBA samples depend in the same manner on spacer thickness as the arsine samples. We also note that, although the previously reported mobilities were at temperatures from 1.5 to 4.2 K, [8][9][10][11][12] the mobility is essentially independent of temperature for temperatures below ϳ5 K and mobilities below ϳ2ϫ10 6 cm 2 /V s. 7,11,16,17 With these extremely high mobility samples, we observed the FQHE with very sharp features, indicative of very high quality material. The carrier density dependence on spacer thickness is also shown in Fig.…”

“…These samples had a moderate V/III ratio of 87 and a spacer thickness ranging from 238 to 525 Å. [8][9][10][11][12] The corresponding 2DEG density was only 3.2ϫ10 11 cm Ϫ2 , significantly lower than densities of previous MOCVD high mobility samples, so that the mobility figure of merit 13,14 (/n 3/2 ) for this sample was 1.1ϫ10 Ϫ11 cm 5 /V s, almost twice that of previously reported 2DEGs grown with arsine. 1 together with mobilities of arsine-grown samples.…”

“…As compared to molecular beam epitaxy ͑MBE͒, MOCVD has advantages including high quality regrowth, ability to rapidly and continuously vary alloy compositions, and low defect densities. We then present results on 2DEGs grown using TBA that exhibit mobilities up to 2.0ϫ10 6 cm 2 /V s. These are the highest mobilities to date for MOCVD materials [8][9][10][11][12] and approach state-of-the-art MBE mobilities. However, there are two primary disadvantages of MOCVD: lower material purity compared to MBE, and safety concerns due to highly toxic arsine gas.…”

“…The dark and light mobilities at 0.3 K for these samples are plotted in Fig. [8][9][10][11] This sample had dark mobilities ͑carrier concentrations͒ at 300, 77, and 0.3 K of 6500 (4.1ϫ10 11 ), 1.8ϫ10 5 (2.8ϫ10 11 ͒, and 1.2ϫ10 6 cm 2 /V s (2.3ϫ10 11 cm Ϫ2 ), respectively. The mobility of the TBA samples depend in the same manner on spacer thickness as the arsine samples.…”

High quality single and double two-dimensional electron gases grown by metalorganic vapor phase epitaxy

“…[9][10][11][12] They have also been used for novel devices including one-dimensional channel field effect transistors 13 and coupled quantum dot arrays. [17][18][19] In this letter, we demonstrate the MOVPE growth of high quality 2DEG structures that exhibit the fractional quantum Hall effect and have the highest mobility figure of merit to date for MOVPE grown material. This is so despite continuing improvements in reactor and source purity, and despite certain advantages over MBE for high mobility applications such as high quality regrowth capability for back gate definition and nanostructure fabrication, 15,16 high growth rates for the needed thick buffer layers, and low defect densities.…”