Characterization of strained GaInAs/AlInAs quantum well TEGFETS grown by molecular beam epitaxy

Defect free strained layer epitaxy opens possibilities for further improvement on the quantum well two-dimensional electron gas FET (TEGFET) structures grown using the GaInAs/AlInAs on InP materials system. Increased freedom with composition allows for optimizing certain properties of the structure, such as, the conduction edge discontinuity which controls the maximum sheet concentration ( n s ); and the electron effective mass which influences the speed of the structure. These enhancements can be made respectively by increasing the Al concentration in the AlInAs and/or by decreasing the Ga concentration in the GaInAs. The maximum amount of strain which can be incorporated into the unrelaxed material sets an upper limit on the compositional tolerances. The tolerances will be shown to be large for the AlInAs and the active TEG GaInAs region. The compositions are obtained using the intensity oscillations observed in the reflection high energy electron diffraction (RHEED) specular beam during growth of GaAs, AlAs, and subsequently GaInAs on GaAs. X-ray rocking curves and photoluminescence (PL) are used to verify the calibrations for growths on InP. The dependency of the mobility on strain is shown. The maximum 300 K mobility obtained was 12,360 cm 2/V·s with n s of 1.25×10 12/ cm 2. The well thickness was 84 nm. The AlInAs and GaInAs were estimated to be +0.04 and +0.17 In fraction from lattice match respectively. A mobility of 11,550 cm 2/V·s was obtained using a 34 nm well. Strong PL (10 K) peaks will be shown from the quantum well TEGFET structures having a full width at half maximum intensity as low as 12.5 meV. The energies are below the GaInAs bandgap energy ranging from 0.69 to 0.80 eV.