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AlGaN/GaN
High-Electron-Mobility
Transistors Grown
by Ammonia Source
Molecular Beam Epitaxy
Yvon Cordier
2.1 INTRODUCTION
Since it has been shown that an AlGaN/GaN heterostructure can generate a two-
dimensional electron gas (2DEG) [1], GaN-based high-electron-mobility transistors
(HEMTs) have been developed and are now established as the most interesting III-
nitride electron devices for high-frequency power amplication as well as power
switching. The reason for this is a combination of many factors [2]: the possibility
of achieving high sheet carrier concentration in the 2DEG (~1 × 10
13
/cm
2
) with a
high saturated velocity (>1.5 × 10
7
cm/s), ...