Successful visualisation of 2D electron gas
Japanese team directly observes 2D electron gas at a GaN-based semiconductor interface
A group at the University of Tokyo, led by Naoya Shibata, in collaboration with Sony, has succeeded in directly observing a 2D electron gas that accumulated at a GaN-based semiconductor interface.
GaN-based devices are used as highly efficient LEDs and laser diodes. Because of their high dielectric breakdown strength and saturated electron velocity, they are expected to be used as next-generation high-frequency devices for communication and as power devices for power conversion.
In particular, GaN HEMTs generate a layer of accumulated electrons called a 2D electron gas at the semiconductor interface. Electrons can move at high speeds in this layer, which makes HEMTs excellent for high-frequency operation.
The details of this 2D electron gas are crucial for the performance of semiconductor devices, and they have been estimated via indirect experiments or theoretical calculations. However, direct observation and confirmation of these phenomena are challenging.
In this study, the research group combined magnetic-field-free atomic resolution STEM (MARS) with a newly-developed tilt-scan system and ultra high-sensitivity, high-speed division-type detector to directly observe the 2D electron gas that accumulated at the GaN/AlInN heterointerface.
The group conducted observations using the atomic resolution differential phase contrast (DPC) method, an atomic-level electromagnetic field observation technique developed by Shibata and others.
They successfully visualised and quantified the 2D electron gas that accumulated in the several-nanometer-wide area of the semiconductor interface. These advances enabled control of the 2D electron gas and are expected to further improve the performance of transistors.
The researchers report that these findings have enabled the development of high-performance high-frequency/power devices that control the 2D electron gas, bringing about innovations in interface analysis and control of semiconductor devices.
'Real-space observation of a two-dimensional electron gas at semiconductor heterointerfaces' by Satoko Toyama et al; Nature Nanotechnology (2023)
