Experimental quantification of wave function and effective mass in quantum confined states of semiconductor

利用光电流光谱和光透射光谱研究了分子束外延设备（MBE）制备的In_<0.53>Ga_<0.47>As/In_<0.52>Al_<0.48>As多量子阱结构（mqw）的量子约束态。三种不同井宽（井宽分别为5、9.4、20nm）的未掺杂MQWs结构的光学电流谱均呈现阶梯状结构，且能清晰地观察到光带间跃迁。利用两个或多个光电流谱和施加偏置电压得到的光电流谱的差值进行仔细分析，在导子带和价子带之间分配了具有相同量子数的允许带间跃迁和具有不同量子数的禁止带间跃迁，并确定了这些子带的本征能。通过拟合子带的实验本征能与包络函数近似，确定了子带偏移量和空穴、电子的有效质量。电子有效质量取决于相应导子带的能量。假设电子有效质量转化为能量的变化较为平缓，且导阱底部的电子有效质量与体的带端有效质量相同，为0.041m_0，则充分考虑了本态能量较少或本态能量较低的子带的能量可靠性，电子有效质量可以用能量的二次函数表示。电子有效质量由0.041m_0提高到0.08m_0。另外，在对阱宽为10 nm的未掺杂mqw结构和两种调制掺杂mqw结构的透射光谱中，观察到这些光谱变得阶梯状，并且允许带间跃迁。对于调制掺杂的样品（1.5x10^<12> cm^<-2> 0.5x10^<12> cm^<-2>），通过MQWs结构内电荷的带填充效应，没有观察到两个基态之间低于费米能级的带间跃迁。在100K-330K温度下测得的光谱的阶梯结构几乎不存在温度依赖性，跃迁能的变化仅依赖于阱层的带隙能。通过对各波函数积分得到的吸收系数的光谱表示了光的透射光谱。利用有效质量等物理性质参数，利用电荷分布泊松方程和包络函数近似模型计算得到的本征能和带间跃迁能与光电流和光传输实验结果吻合较好，并且能够对In_<0.53>Ga_<0.47> as /In_<0.52>Al_<0.48> as mqw进行波函数和有效质量的量化。少

Quantum confined states of the In_<0.53>Ga_<0.47>As/In_<0.52>Al_<0.48>As multi-quantum well structures (MQWs) fabricated with molecular beam epitaxy equipment (MBE) were studied using the photocurrent spectroscopy and the optical transmission spectroscopy.The optical current spectra of three kinds of undoped MQWs structures, which had different well width (each well width 5, 9.4, 20nm), showed steplike structure and optical interband transitions were observed clearly. In the careful analysis using two or more photocurrent spectra and the difference of those obtained by applying bias voltage, allowed interband transitions having same quantum numbers and forbidden interband transitions having different quantum numbers were assigned between conduction subband and valence subband and eigen-energies of these subbands had been determined. By fitting the experimental eigen-energies of the subbands to the envelope function approximation, and band offset and effective mass of hole, and electron … More to a normal direction to the MQWs layers are determined. It depended for electron effective mass on the energy of corresponding conduction subband. When it assumes that electron effective-mass changes gently to energy and this mass at the bottom of a conduction well was 0.041m_0 as much as as the effective mass at the bandedge end of bulk, the energy dependability of subband with the small number or low eigen-energy can also fully be taken into consideration, and electron effective mass can be expressed with the secondary function of energy. Electron effective mass was increased from 0.041m_0 to 0.08m_0.Also in the optical transmission spectroscopy to a undoped MQWs structure and two kinds of modulation-doped MQWs, structure with 10 nm well width, these spectra became steplike and allowed interband transitions were observed. About the modulation-doped specimens (1.5x10^<12> cm^<-2> 0.5x10^<12> cm^<-2>) the interband transitions between both ground states which were lower than Fermi Level were not observed by band filling effect of the electric charge within the MQWs structure. There is almost no temperature dependability in the steplike structure of the spectra measured at the temperature of 100K-330K, and the changes of transition energies were only dependent on the band gap energy of a well layer. Moreover, the, spectra of the absorption coefficient by integration of each wave function have expressed the optical transmission spectra.The eigen-energy and the interbnad transition energy, which were calculated with the Poisson equation of an electric charge distribution and envelope function approximation model using physical-properties parameters, such as effective mass, well agreed with an photocurrent and optical transmission experiment and the quantification of the wave function and effective mass were able to perform on the In_<0.53>Ga_<0.47>As/In_<0.52>Al_<0.48>As MQWs. Less