Refractory two-dimensional hole gas on hydrogenated diamond surface

Abstract

Use of two-dimensional hole gas (2DHG), induced on a hydrogenated diamond surface, is a solution to overcoming one of demerits of diamond, i.e., deep energy levels of impurities. This 2DHG is affected by its environment and accordingly needs a passivation film to get a stable device operation especially at high temperature. In response to this requirement, we achieved the high-reliability passivation forming an Al2O3 film on the diamond surface using an atomic-layer-deposition (ALD) method with an H2O oxidant at 450 °C. The 2DHG thus protected survived air annealing at 550 °C for an hour, establishing a stable high-temperature operation of 2DHG devices in air. In part, this achievement is based on high stability of C-H bonds up to 870 °C in vacuum and above 450 °C in an H2O-containing environment as in the ALD. Chemically, this stability is supported by the fact that both the thermal decomposition of C-H bonds and reaction between C-H bonds and H2O are endothermic processes. It makes a stark contrast to the instability of Si-H bonds, which decompose even at room temperature being exposed to atomic hydrogen. In this respect, the diamond 2DHG devices are also promising as power devices expectedly being free from many instability phenomena, such as hot carrier effect and negative-bias temperature instability, associated with Si devices. As to adsorbate, which is the other prerequisite for 2DHG, it desorbed in vacuum below 250 °C, and accordingly some new adsorbates should have adsorbed during the ALD at 450 °C. As a clue to this question, we certainly confirmed that some adsorbates, other than those at room temperature, adsorbed in air above 100 °C and remained at least up to 290 °C. The identification of these adsorbates is open for further investigation.

Reduction of interface states by hydrogen treatment at the aluminum oxide/4H-SiC Si-face interface

“…The difference in capacitance for the plasma ALD samples was larger than that for the thermal ALD samples, probably because the O plasma destroys the plasma-pretreated SiC-surface condition. Hiraiwa et al reported that the condition of the substrate surface is preserved after thermal ALD, 24 which is consistent with the present results. Therefore, it was concluded that the O plasma process must be excluded, and we instead a combination of H plasma pretreatment and thermal ALD was adopted.…”

Ohmic contact between iridium film and hydrogen-terminated single crystal diamond

“…As the annealing temperature increases, the linear slope decreases shown in Fig. 3(a), indicating the increase of resistance between the measured Au/Ir electrodes, which could be attributed to the reduction of absorption and H-termination bonds on the diamond surface during annealing process 32,33 . Linear fitting curves of the same TLM pattern at different annealing temperatures of sample A shown in Fig.…”

Active and fast charge-state switching of single NV centres in diamond by in-plane Al-Schottky junctions

“…7 and diode properties respectively after many switching cycles is due to the interaction of the H-terminated diamond surface with air, particularly with oxygen (O 2 ) and ozone (O 3 ) [29]. This interaction is catalysed by illumination of the surface with laser light and application of potential on the diode.…”

“…Since the stability of the two-dimensional hole channel is influenced by the interaction with the atmosphere, the H-terminated diamond surface need to be passivated to get a stable device operation and NV manipulation. One passivation method was suggested by Hiraiwa et al by covering the surface with an Al 2 O 3 film using an atomic-layer-deposition (ALD) method with an H 2 O oxidant at 450 °C [29]. They could show that this film does not destroy the C–H bonds as well as the atmospheric adsorbate layer on top of the H-terminated surface which is required for the generation of a two-dimensional hole channel.…”