INCREASED ELECTRON-CONCENTRATION IN INAS ALGASB HETEROSTRUCTURES USING A SI PLANAR-DOPED ULTRATHIN INAS QUANTUM-WELL/

Mie demonstrate that the two-dimensional electron gas concentration in an InAs/AlGaSb heterostructure can be greatly increased by introducin g a Si planar-doped ultrathin InAs quantum well (QW) sandwiched betwee n AlSb barriers as an additional electron supplying layer in a well co ntrolled fashion. With the Si planar-doped QW formed 8 nm below the ch annel 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 77 K. S hubnikov-de Haas measurements revealed that only two subbands are occu pied, even for heavily doped samples. The energy separation between th e first and the second subbands is as large as 100 meV, indicating a s trong electron confinement in the selectively doped InAs/AlGaSb hetero structures.