AlGaN/GaNヘテロ界面に形成される2次元電子ガスの光学的特性

概要

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AlGaN/GaN hetero-structures have attracted much attention for their novel device applications. It is also known that a two-dimensional electron gas (2DEG) layer is formed by an accumulation of carriers due to a strong piezoelectric field in a distorted AlGaN layer at the interface. For the optical properties of the 2DEG, only a few reports on the photoluminescence (PL) measurements were published. No thorough discussion of the carrier transition mechanism is studied yet. We have then carried out the PL and surface photovoltage (SPV) measurements. Although the observed 2DEG signals in the PL spectra disappeared above 50K, SPV signal still existed even in the room temperature spectra. Since the SPV can detect the additional photo-induced electric field, the transition mechanism including carrier drift and accumulation can be discussed. The activation energy for the electron occupation was estimated at 9.3 meV from the SPV spectra. Therefore, the quantized level located 50meV, which is calculated by the PL results, below the conduction band may not directly contribute the signal. The Fermi energy in the quantum well should take into account for further discussion.
宮崎大学の論文
2008-08-30