Abstract: Lattice-mismatched heterogeneous semiconductor grafting technique has been developed recently to combine lattice-mismatched semiconductors and create innovative devices. An ultrathin oxide (UO) deposited by atomic layer deposition (ALD) at the grafted interface has been recognized as a passivation and tunneling layer, which plays an important role in improving the junction performance, such as achieving higher on/off ratio and lower ideality factor in a pn junction. To better understand the influence of the ALD UO, various experiments have been conducted to characterize some electrical properties of the ALD UO in various semiconductor systems. In the first part of the presentation, the history of semiconductor heterostructures and the development of semiconductor grafting technique are reviewed. In the second part, the interfaces between the UO and several semiconductors were characterized by X-ray photoelectron spectroscopy (XPS). Various electron states were observed through peak fitting. The correlation between the passivation effect and the electron states was established. In the third part, the surface band-bending of c-plane Ga-face GaN with various UO/UN layers was characterized by XPS measurements. The valence band offset (VBO) between GaN and the UO/UN was calculated from the GaN valence band spectra. The possibility of fabricating an AlGaAs/GaAs/GaN npn heterojunction bipolar transistor (HBT) was examined through simulation. In the last part, a novel releasing and transfer printing method of the single-crystalline AlN nanomembrane (NM) was introduced. The properties of the AlN were characterized both before and after the whole process and no degradation was observed. The possibility of obtaining high-quality single-crystalline AlN NM brings new potentials to the semiconductor grafting technique.