Increased Electron Concentration in InAs/AlGaSb Heterostructures Using a Si Planar Doped Ultrathin InAs Quantum Well

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Abstract
We demonstrate that the two-dimensional electron gas concentration in an InAs/AlGaSb heterostructure can be greatly increased by introducing a Si planar-doped ultrathin InAs quantum well (QW) sandwiched between AlSb barriers as an additional electron supplying layer in a well controlled fashion. With the Si planar-doped QW formed 8 nm below the channel layer, the sheet electron concentration increased up to 4.5×1012 cm-2 with an electron mobility of 4×104 cm2/ Vs at 77 K. Shubnikov-de Haas measurements revealed that only two subbands are occupied, even for heavily doped samples. The energy separation between the first and the second subbands is as large as 100 meV, indicating a strong electron confinement in the selectively doped InAs/AlGaSb heterostructures.