Separate Evaluation of Electron Coherence Influence Factors in Quantum Device by Resonant Tunneling Structures

为了阐明利用共振隧道二极管(RTD)的IV特性分别评价电子相干性的影响因素，即相位驰豫、结构不均匀和温度的可能性，提出了一种利用RTD的IV特性来评价电子相干性的方法。该方法将IV曲线分为三个区域，即a)电流截止区、b)电流上升区和c)电流峰区。通过完全拟合实验测量的IV曲线，可以分别从a)区和b)区评估电子相干性和结构不均匀性。为了验证本方法的有效性，我们对采用阶跃流动模式生长的InP/InGaAsRTD进行了评估。假设势垒宽度起伏为0.6 nm，对4.2K下测量的IV数据进行了从a)到c)三个数量级的完全拟合，证实了我们所提出的方法的有效性。然后，我们发现了对a)区影响很小的条件。例如，当掺杂浓度为3×10^&lt；17&gt；cm^&lt；-3&gt；时，用长度为2.6 nm的隔离层抑制了这种影响。最后，利用目前所得到的理论方法，我们成功地给出了一种可以单独计算电子相干性的RTD结构。

The objective of the research is to clarify a possibility to separately evaluate electron coherence influence factors, that is, phase relaxation, structural inhomogeneity, and temperature, by using IV characteristics of resonant tunneling diode(RTD).We proposed an evaluation method of electron coherence by IV characteristics of RTD. In the method, IV curves are divided into three regions, that is, a)current cut-off region, b)current raising region, and c)current peak region. By fitting experimentally measured IV curve completely, electron phase coherence and structural inhomogeneity can be evaluated from region a)and b)respectively.To confirm effectiveness of present method, we evaluated a InP/InGaAs RTD which was grown by the step flow mode. IV data measured at 4.2K was completely fitted over three orders in current magnitude from region a)to c)by assuming well width fluctuation of 0.6 nm, and we confirmed the effectiveness of our proposed method.Next, we modeled the influence of random distribution of impurities in the emitter and collector electrodes on IV characteristics. Then, we found the condition that the influence on the a)region was quite small. For example, the influence was suppressed with a spacer layer of length 2.6nm when a doping density was 3x10^<17>cm^<-3>.Finally, by using the theoretical method obtained thus far, we succeeded to give a RTD structure where the electron coherence could be evaluated separately.