掺杂在GaAs材料中Be受主能级之间的跃迁

Transitions between Be acceptor levels in GaAs bulk

通过远红外吸收谱、光致发光光谱和拉曼散射光谱,对均匀掺杂在GaAs材料中Be受主能级之间的跃迁进行了研究.实验中使用的GaAs:Be样品是通过分子束外延设备,生长在半绝缘(100) GaAs衬底之上的外延单层.在4.2 K温度下,对样品分别进行了远红外吸收光谱、光致发光光谱、Raman光谱的实验测量.在远红外吸收光谱中,清楚地观察到了从Be受主1S3/2Γ8基态到它的三个激发态2P3/2Γ8, 2P5/2Γ8和2P5/2Γ7之间的奇宇称跃迁吸收峰.跃迁能量与先前文献中报道的符合得很好.从光致发光光谱中,观察到了Be受主从1S3/2Γ8基态到2S3/2Γ8激发态的两空穴跃迁的发光峰,从而间接地找到了两能级之间的跃迁能量.在Raman光谱中,清楚地分辨出来了Be受主从1S3/2Γ8基态到2S3/2Γ8激发态偶宇称跃迁的拉曼散射峰,直接得到了两能级间的跃迁能量.对比发现,分别直接和间接得到的1S3/2Γ8基态到2S3/2Γ8激发态跃迁能量结果是一致的.

The doping is one of important means in the semiconductor manufacturing techniques, by which the optical and electric properties of semiconductor materials can be significantly improved. The doping level and energy level structure of dopants have a great influence on the operating performances of micro-electronic devices.Beryllium is one of acceptors, which is frequently used to be doped in GaAs bulk, because it is very stable with respect to diffusion at higher temperatures. Therefore, it is significant for the application to optoelectronic devices that the energy-state structure of Be acceptors in GaAs bulk can be investigated in detail. The sample GaAs:Be used in experiment is a 5-μm-thick epitaxial single layer doped uniformly by Be acceptors with a doping level of 2 × 1016 cm–3, and grown by molecular beam epitaxy on 450-μm-thick semi-insulating(100)GaAs substrates in a VG V80 H reactor equipped with all solid sources. The transitions between the energy states of Be acceptors are studied experimentally by different spectroscopy techniques. The far-infrared absorption experiments are performed by using a Fourier-transform spectrometer equipped with a tungsten light source and a multilayer wide band beam splitter. Prior to the absorption spectrum measurement, the sample is thinned, polished and wedged to approximately a 5° angle to suppress optical interference between the front and back faces. Then, the sample is placed into the cryostat with liquid helium(4.2 K). The photoluminescence and Raman spectra are also measured at 4.2 K by a Renishaw Raman imaging microscope. The optical excitation to the sample is provided by an argon-ion laser with a wavelength of 514.5 nm, and the excited power is typically5 mW. The odd-parity transitions from the Be acceptor ground state 1 S3/2 G8 to three excited states, i.e. 2 P3/2 G8,2 P5/2 G8 and 2 P5/2 G7 are clearly observed in the far-infrared absorption spectra, then the respective transition energy values are obtained, which are in excellent agreement with the experimental results reported previously.In the photoluminescence spectrum, the emission peak labelled two hole transition, originating from the twohole transition of recombination of the neutral-accptor bound excitons, is seen obviously, thus the energy of the even-parity transition between 1 S3/2 G8 and 2 S3/2 G8 states is found indirectly. Furthermore, in the Raman spectrum measured, the transition peak between 1 S3/2 G8 and 2 S3/2 G8 states is well resolved, and the transition energy between them is gained directly. By comparison, the transition energy values gained directly and indirectly are found to be consistent with each other.