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The cubic BN (c-BN)/diamond heterostructure proposed recently to possess 2-D electron gas (2DEG) could be a solution to diamond n-type field-effect transistors (FETs). However, the growth of c-BN/diamond system is still challenging. This work theoretically investigates the electronic transport property of c-BN/diamond heterostructure and explores its potential in electronic devices fields. The 2DEG sheet density in the heterointerface is calculated considering the effects of Schottky barrier height and modulation doping (MD) in c-BN barrier layer. The 2DEG mobility is the sum of five possible scattering mechanisms. The results show that the 2DEG mobility of c-BN/diamond heterostructure could be higher than 3000 cm2/ $\text {V}\cdot \text { s}$ at room temperature for 2DEG sheet density of $\sim 10^{{12}}$ cm−2 with a Schottky barrier of 1.1 eV and the undoped c-BN barrier thickness of 20 nm. Acoustic phonon (AC) scattering is the main scattering mechanism of the 2DEG for relatively large range of the c-BN layer thickness at room temperature. Remote surface roughness (RSR) scattering could dominate with very thin c-BN layer (<6 nm) if dense 2DEG was available even without MD, or otherwise, the MD scattering could dominate for thin c-BN layer if 2DEG mainly originated from the doping ionization. The temperature-dependent 2DEG mobility is determined by the phonon scatterings for temperature higher than ~100 K.

Hydrogenated silicon-doped (Si-doped) diamond was prepared by magnetron sputtering silicon on IIa CVD diamond surface and following Si etch/diffuse process at 1000 °C in a hydrogen atmosphere in MPCVD. The silicon doping concentration was higher than $1\times 10^{{18}}$ cm−3 among the depth of 25 nm. The hydrogenated Si-doped diamond surface demonstrated the simultaneous presence of C–H and C–Si bonds in the X-ray photoelectron spectroscopy (XPS) results, and a square resistance of 5500 $\Omega $ /sq with the hole concentration of $1.4\times 10^{{13}}$ cm−2 by contact Hall test. MOSFET fabricated on the hydrogenated Si-doped diamond using traditional hydrogenated diamond device process showed decent device performance. The gold/hydrogenated Si-doped diamond electrodes showed ohmic contact resistivity of $1.02\times 10^{-{5}}\,\,\Omega \cdot $ cm−2 and a contact resistance of 2.4 $\Omega \cdot $ mm. Besides, the 1.5- $\mu \text{m}$ MOSFET device with a threshold voltage of 1.4 V delivered the maximum drain current, ON-resistance, maximum transconductance, and ON/ OFF ratio of −270.5 mA/mm, 39.6 $\Omega \cdot $ mm, 42.4 mS/mm and 8 orders of magnitude. The gate breakdown field and the OFF-state source-drain breakdown field reached 8.4 and 2.17 MV/cm, respectively. The hydrogenated Si-doped diamond provided a promising route for the preparation of high-performance diamond FET devices.

Radiation detectors are important device-level characterization tools of the carrier dynamics of diamond as an ultrawide-bandgap semiconductor. Herein, a high-quality single-crystal diamond was grown on a high-temperature and high-pressure diamond substrate through microwave plasma chemical vapor deposition. We achieved the enhancement of microwave power density by compressing a plasma ball and optimizing the carbon-hydrogen ratio (C/H) within the plasma and thus considerably diminished the impurity and dislocation densities of the diamond epilayer. The full width at half maximum of the X-ray (004) reflection rocking curve was 15 arcsec, and no impurity emission bands were detectable in the photoluminescence spectrum at room temperature (25°C). The radiation detector made from this 200-µm-thick diamond epifilm demonstrated an α-particle response with a charge collection efficiency of 97.03% and energy resolutions of 2.1% for electrons and 97.86% and 1.5% for holes. Furthermore, the product of mobility and lifetime of electrons and holes reached 8 × 10−5and 4.1 × 10−4cm2V−1, respectively. The epitaxial method reduces costs while fulfilling the stringent requirements of radiation detection for commercial applications.

We report on achieving high conductivity hydrogenated boron (B) and silicon (Si) co-doped diamond with a room-temperature Hall result of a square resistance of 2724 ohm/sq, a sheet hole density of ${3}.{3}\times {10} ^{{13}}$ cm−2, and a hole mobility of 68.9 cm2/Vs. The co-doping of B and Si is realized in such a way. First, etch solid BN disk by hydrogen plasma in microwave plasma chemical vapor deposition (MPCVD) system to form B source, and sputter Si film on the diamond surface, and then etch the Si film on diamond sample by hydrogen plasma at 1000 °C in the same MPCVD chamber, and B/Si diffuse to dope diamond. The secondary ion mass spectroscopy of the sample shows that at a depth of $0.3~\mu \text{m}$ , the B and Si doping concentration is higher than ${1}.{0}\times {10} ^{{17}}$ cm−3, and the highest B and Si doping concentration at the surface is ${3}.{7}\times {10} ^{{20}}$ cm−3 and $^{} {1}.{1}\times {10} ^{{20}}$ cm−3, respectively. By using Au to form the ohmic contact electrode, the sample achieves the low ohmic contact resistance of $0.46~\Omega \cdot $ mm and the contact resistivity of ${1}.{6}\times {10} ^{-{5}}\,\,\Omega \cdot $ cm2. The B and Si co-doped diamond provides a new idea for the ohmic contact process optimization of diamond FET devices.

The extremely low leakage, fast response, and excellent thermal conductivity of diamond facilitate its potential application in pulse power switching devices. In this study, we investigated the static and transient characteristics of diamond avalanche diodes (DADs) via 2-D device simulation. DAD is based on a Schottky barrier diode (SBD) structure. The static breakdown voltage is 590 V. Under an input pulse voltage with a peak voltage of 2400 V and a rise time of 2 ns, the output voltage on a 50- $\Omega $ load driven by the device has a peak value of 1.83 kV and a rise time of 1.282 ns. The behavior and mechanism of the sharpened rising pulse response waveform are analyzed phase by phase. The generation and dynamic changes in carrier plasma inside the device and their effect on the altered electric field, impact generation, and carrier density, as well as the transient output of the device are investigated.

Hydrogen-terminated diamond (H-diamond) field-effect transistors (FETs) have been the mainstream structure of diamond microwave devices. In this article, the direct current performance and cutoff frequency ( ${f}_{T}$ ) of H-diamond FETs with the gate length ( ${L}_{G}$ ) downscaling from $2 ~\mu \text{m}$ to 50 nm are investigated by 2-D device simulation. For our central-gated device with a 6-nm-thick Al2O3 gate dielectric, the transition point of ${L}_{G}$ from the long-channel behavior to the short-channel one is found to be about 200 nm. Though notable short-channel effects appear for ${L}_{G} \le {200}$ nm such as the negative shift of the threshold voltage and the increase of the drain-induced barrier lowering, the knee voltage at a given gate voltage stays almost constant for all the considered gate length range, which is unfavorable for a small-size device with lower operating voltage. It is found the effective velocity in the channel of short-channel H-diamond FETs at the drain voltage of 7 V is less than half of the saturation velocity. The ${f}_{T}$ versus ${V}_{\text {GS}}$ relation is quite different in the short channel case and long channel case, and it is analyzed in comparison with the ${g}_{m}$ versus ${V}_{\text {GS}}$ relation.

The cascode structure was fabricated by combining the H-diamond normally-ON p-FET with the Si normally-OFF p-FET. The cascode shows normally- OFF characteristics with the threshold voltage of −0.8 V and the maximum transconductance of 344.6 mS/mm. The maximum saturation drain current and minimum ON-resistance are 34.2 mA/mm and $18.74 ~\Omega \cdot $ mm, respectively. In addition, the cascode structure can work as an inverter. The voltage transfer characteristics (VTCs) and dynamic switching characteristics at the frequency of 200 Hz of the diamond cascode inverter were demonstrated first. These results indicate that the diamond cascode is suitable to be used to achieve diamond normally- OFF device and can also be used to work as the inverter.