Compound semiconductors
Why is the conducting layer formed by hydrogen-terminating the surface being studied as a channel for diamond semiconductor transistors?
- AA thin layer of holes forms just below the surface, allowing p-channel transistors that avoid the problem of deep dopant levels
- BHydrogen termination reduces diamond's bandgap to 0 eV and makes it a metal
- CHydrogen termination makes it easy to form n-type layers
Show answer and explanation
Answer: A. A thin layer of holes forms just below the surface, allowing p-channel transistors that avoid the problem of deep dopant levels
In a diamond semiconductor, boron and phosphorus levels are deep, so it is hard to obtain enough carriers at room temperature. When the surface is hydrogen-terminated, electron exchange with adsorbed substances forms a two-dimensional hole gas just below the surface. Adsorbing NO2 or similar molecules raises the hole density, and p-channel MOSFETs using this layer as the channel are being studied. In 2023 Saga University announced the operation of a power circuit using diamond MOSFETs with holes induced by NO2.
- A. Correct. A conducting layer forms without relying on dopants.
- B. The bandgap does not change; a hole layer simply forms below the surface.
- C. The layer that forms is a hole layer, not an n-type layer.