The detection of terahertz waves by semimetallic and by semiconducting materials

摘要

We present a survey of photoresponse (PR) measurements of various devices containing quantum wells (QWs) of HgTe of various widths dQW and of InSb. By varying dQW for HgTe, the material properties of the QW material change from semiconducting to semimetallic as dQW is increased above a value of about 6nm. We have studied the PR of devices made from CdxHg1−xTe/HgTe/CdxHg1−xTe wafers with values of the QW width in the range of 6 nm ≤ dQW ≤ 21 nm. Only for samples with semimetallic HgTe QWs, a measurable PR could be detected. However, our investigations of samples made from AlxIn1−xSb/InSb/AlxIn1−xSb wafers gave evidence that a measurable PR also can appear from devices with a semiconducting QW. Both cyclotron-resonant (CR) and nonresonant (bolometric, BO) interaction mechanisms can contribute to the PR signal. Whereas the CR contribution is dominant in AlxIn1−xSb/InSb/AlxIn1−xSb samples, in CdxHg1−xTe/HgTe/CdxHg1−xTe samples the behavior is more complex. In a sample with dQW = 8 nm, the PR is clearly dominated by the BO contribution. In the PR of another sample of dQW = 12 nm, both contributions (BO and CR) are present. The sample of dQW = 21 nm shows a PR with not clearly separable BO and CR contributions.