1.School of Space Science and Physics, Shandong University (Weihai), Weihai 264209, China 2.School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China 3.School of Information Engineering, Shandong University (Weihai), Weihai 264209, China 4.Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China 5.Jinan Semiconductor Research Institute, Jinan 250014, China
Fund Project:Project supported by the Natural Science Foundation of Shandong Province, China (Grant No. ZR2017MF018) and the National Natural Science Foundation of China (Grant No. 61675223)
Received Date:26 February 2019
Accepted Date:29 June 2019
Available Online:01 September 2019
Published Online:20 September 2019
Abstract: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 typically 5 mW. The odd-parity transitions from the Be acceptor ground state 1S3/2Γ8 to three excited states, i.e. 2P3/2Γ8, 2P5/2Γ8 and 2P5/2Γ7 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?holetransition, originating from the two-hole transition of recombination of the neutral-accptor bound excitons, is seen obviously, thus the energy of the even-parity transition between 1S3/2Γ8 and 2S3/2Γ8 states is found indirectly. Furthermore, in the Raman spectrum measured, the transition peak between 1S3/2Γ8 and 2S3/2Γ8 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. Keywords:far-infrared absorption spectrum/ Raman spectrum/ photoluminescence spectrum/ energy state structure of Be acceptor
图 1 掺杂在GaAs材料中Be受主的能级分布及跃迁
图 2 在4.2 K温度下, GaAs:Be样品的远红外吸收谱
图 3 在4.2 K温度下, GaAs:Be样品的PL光谱
图 4 在4.2 K温度下, GaAs:Be样品的Raman光谱