超高真空扫描隧道谱实验对碲镉汞室温带隙的直接测定

Band gap determination of HgCdTe by ultra high vacuum scanning tunneling spectroscopy

利用超高真空扫描隧道显微镜的隧道谱实验对汞空位掺杂的液相外延P型碲镉汞材料在室温条件下进行测量,发现直接的电流-电压隧道谱对带隙预言一定程度上要受到成像偏置电压的影响.但当采用了锁相放大测量技术,通过实验直接获取微分隧道谱(dI/dV)信号,并利用电流-电压谱对dI/dV作归一化处理时,最终结果则能较准确、可靠地预言材料的带隙,表明扫描隧道谱方法作为独立于光学方法之外的另一种实验表征手段对碲镉汞能带电子结构研究的适用性.

In contrast to conventional band gap determination of Hg1-xCdxTe by lowtemperature Fourier transform spectroscopy, we report the application of tunneling spectroscopy （ STS ） technique to measure the energy band gap of the vacancy-doped P-Hgl.xCdxTe grown by liquid-phase epitaxy （LPE） method. The apparent zero-current gaps measured by current-voltage tunneling spectroscopy are influenced by the imaging bias. However, the real energy band gap can be revealed by the normalized differential tunneling conductance, which were obtained using the lock-in amplifier technique. The results indicate the feasibility of room temperature band gap determination by the STS technique.