| The crystal and electrical properties of the Tm(As, P)/GaAs and GaAs, P)/Tm(As, P)/GaAs heterostructures grown by molecular-beam-epitaxy have been investigated. Single-crystal thulium arsenide-phosphide (Tm(As, P)) films have been grown heteroepitaxially on (001) GaAs substrates by molecular beam epitaxy (MBE) with the orientation relationship [100] Tm(As, P) // [100] GaAs and {lcub}001{rcub} Tm(As, P) // {lcub}001{rcub} GaAs. Good epilayer quality was demonstrated through x-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM) analyses. Tm(As, P)/GaAs structures show good Schottky behavior.; Microtwin-like planar defects were observed in {lcub}111{rcub} and {lcub}224{rcub} planes by transmission electron microscopy. The microtwin found here is strongly affected by the growth conditions. The occurrence of the observed microtwins in TmP/GaAs can be accounted for by the growth-accident mechanism, where the formation of microtwins is via growth accident in the stacking sequence on {lcub}111{rcub} and {lcub}112{rcub} planes.; In this study, it was found that the addition of Tm yields a tremendous improvement in surface morphology of Ga(As, P) overlayer on Tm(As, P)/GaAs. The use of Tm doping shows promise for improving the Ga(As, P) wetting of Tm(As, P) surfaces. Even under high growth rates (>0.6μm/hr) and high growth temperatures (>600°C), a mirror-like smooth surface can still be obtained. The improvement in the surface morphology with Tm doping is primarily due to the increasing density of Ga(As, P) nuclei in the early stage of growth. This offers an attractive way of fabricating the monolithic metal-base-transistor (MBT) with a metal-insulator-metal-semiconductor (MIMS) structure. Indeed, the current-voltage characteristics of these devices exhibit transistor behaviors. A likely model for the emission mechanism is proposed. Besides monolithic MIMS transistors, MBTs with a semiconductor-metal-semiconductor (SMS) structure have been fabricated through wafer-bonding technique. From the I–V measurements, a common base current gain α ≈ 0.55 measured at VCB = 0 was obtained at room temperature.; This study identified the material issues that currently limit the device performance and offered different approaches to obtain better material quality and to realize metal base transistors. Also, this study suggested work for future device improvement. It is hoped that further progress could be made in future device applications. |
