Fabrication of three-dimensional GaAs–AlGaAS heterostructures for improving carrier injection efficiency in quantum-wire FETs

Three-dimensional (3D) GaAs–AlGaAS heterostructures were grown by selective-area molecular beam epitaxy on a patterned GaAs(0 0 1) substrate to improve the efficiency of carrier transport from the source to the drain through 1D channels in quantum-wire (QWR) field-effect transistors. Prior to the QWR growth, GaAs ridge structures with 2 μm line-and-space patterns, were prepared as the starting materials. The surface of the ridge was chemically treated with an NH3 solution to improve the surface roughness and thereby to minimize the defect density at the GaAs/AlGaAs interface. Then, GaAs/AlGaAs QWRs were grown on top of the ridge structures with optimum growth conditions. A scanning electron microscope and position-resolved μ-PL measurements along the QWR direction showed that 3D GaAs–AlGaAS heterostructures, where 1D QWRs were adiabatically coupled with a 2D electron gas, were successfully fabricated.