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

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 8nm below the channel layer, the sheet electron concentration increased up to 4.5 x 10 12 cm -2 with an electron mobility of 4 x 10 4 cm 2 /Vs at 77K. 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.