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The two-dimensional hole gas (2DHG) induced at H-terminated diamond surface provides the most widely used room-temperature surface electrical conductance of diamond semiconductors. Temperature and hole sheet density dependences of the mobility of 2DHG in H-terminated diamond are investigated for the first time considering four scattering mechanisms: surface impurity (SI) scattering, acoustic deformation potential (AC) scattering, nonpolar optical phonon (NOP) scattering, and surface/interface roughness (SFR/IFR) scattering. The calculation results are then compared with the experimental data, where the best agreement is obtained with the effective coupling constant of the non-polar optical phonon D nop and the correlation length L with values of of 1.2 Â 10 10 eV cm À1 and 2 nm, respectively. The theoretical data show that the SI scattering dominates the 2DHG mobility at a relatively large range of the temperature and the hole density due to the proximity of the surface impurities to the 2DHG, while the NOP scattering becomes important as the temperature increases further.

Hydrogen-terminated diamond (H-diamond) metal-oxide-semiconductor field effect transistors (MOSFETs) were fabricated on a polycrystalline diamond substrate. The device has a gate length of 2 μm and uses Al2O3 grown by atomic layer deposition at 300 °C as a gate dielectric and passivation layer. The Al2O3/H-diamond interfacial band configuration was investigated by X-ray photoelectron spectroscopy, and a large valence band offset (3.28 eV) that is very suitable for p-channel H-diamond FETs was observed. Meanwhile, the measured O/Al ratio hints that there are Oi or VAl defects in the Al2O3 dielectric, which can work as an acceptorlike transfer doping material on a H-diamond surface. The device delivers the maximum saturation drain current of over 200 mA/mm, which is the highest for 2-μm H-diamond MOSFETs with the gate dielectric or passivation layer grown at 300 °C or higher temperature. The ultrahigh on/off ratio of 1010 and ultralow gate leakage current of below 10−12 A have been achieved. The high device performance is ascribed to the ultrahigh carrier density, good interface characteristics, and device processes. In addition, the transient drain current response of the device can follow the gate voltage switching on/off pulse at a frequency from 100 kHz to 1 MHz, which indicates the potential of the H-diamond FETs in power switch applications.

77 K micro-photoluminescence spectrum, room-temperature near-field photoluminescence image, and a local atomic arrangement of the nitrogen-vacancy (NV) center in diamond.