Single crystal diamond membranes for nanoelectronics.

Single crystal, nanoscale diamond membranes are highly sought after for a variety of applications including nanophotonics, nanoelectronics and quantum information science. However, so far, the availability of conductive diamond membranes has remained an unreachable goal. In this work we present a complete nanofabrication methodology for engineering high aspect ratio, electrically active single crystal diamond membranes. The membranes have large lateral directions, exceeding ∼500 × 500 µm2 and are only several hundreds of nanometers thick. We further realize vertical single crystal p-n junctions made from the diamond membranes that exhibit onset voltages of ∼10 V and a current of several mA. Moreover, we deterministically introduce optically active color centers into the membranes, and demonstrate for the first time a single crystal nanoscale diamond LED. The robust and scalable approach to engineer the electrically active single crystal diamond membranes offers new pathways for advanced nanophotonic, nanoelectronic and optomechanical devices employing diamond.

Direct Nanoscale Sensing of the Internal Electric Field in Operating Semiconductor Devices Using Single Electron Spins.

The electric field inside semiconductor devices is a key physical parameter that determines the properties of the devices. However, techniques based on scanning probe microscopy are limited to sensing at the surface only. Here, we demonstrate the direct sensing of the internal electric field in diamond power devices using single nitrogen-vacancy (NV) centers. The NV center embedded inside the device acts as a nanoscale electric field sensor. We fabricated vertical diamond p-i-n diodes containing the single NV centers. By performing optically detected magnetic resonance measurements under reverse-biased conditions with an applied voltage of up to 150 V, we found a large splitting in the magnetic resonance frequencies. This indicated that the NV center senses the transverse electric field in the space-charge region formed in the i-layer. The experimentally obtained electric field values are in good agreement with those calculated by a device simulator. Furthermore, we demonstrate the sensing of the electric field in different directions by utilizing NV centers with different N-V axes. This direct and quantitative sensing method using an electron spin in a wide-band-gap material provides a way to monitor the electric field in operating semiconductor devices.

Inversion channel diamond metal-oxide-semiconductor field-effect transistor with normally off characteristics.

We fabricated inversion channel diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) with normally off characteristics. At present, Si MOSFETs and insulated gate bipolar transistors (IGBTs) with inversion channels are widely used because of their high controllability of electric power and high tolerance. Although a diamond semiconductor is considered to be a material with a strong potential for application in next-generation power devices, diamond MOSFETs with an inversion channel have not yet been reported. We precisely controlled the MOS interface for diamond by wet annealing and fabricated p-channel and planar-type MOSFETs with phosphorus-doped n-type body on diamond (111) substrate. The gate oxide of Al2O3 was deposited onto the n-type diamond body by atomic layer deposition at 300 °C. The drain current was controlled by the negative gate voltage, indicating that an inversion channel with a p-type character was formed at a high-quality n-type diamond body/Al2O3 interface. The maximum drain current density and the field-effect mobility of a diamond MOSFET with a gate electrode length of 5 µm were 1.6 mA/mm and 8.0 cm(2)/Vs, respectively, at room temperature.