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

为了阐明利用共振隧穿二极管（RTD）的IV特性分别评价电子相干性影响因素（相位弛豫、结构不均匀性和温度）的可能性，提出了一种利用RTD的IV特性评价电子相干性的方法。在该方法中，IV曲线分为三个区域，即，a）电流截止区域，B）电流升高区域，和c）电流峰值区域。通过对实验测得的IV曲线的完全拟合，可以分别从a）和B）区域评价电子相位相干性和结构不均匀性。在假设阱宽波动为0.6 nm的情况下，对4.2K下测得的IV数据进行了3个数量级的拟合，验证了所提出方法的有效性。然后，我们发现了对a）区域的影响很小的条件。例如，当掺杂浓度为3 × 10 ~（-3）cm ~ 3时，间隔层长度为2.6nm时，这种影响被抑制<17>了<-3>。最后，利用目前得到的理论方法，我们成功地给出了一种可以单独评估电子相干性的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.