Bipolar persistent photoconductivity in HgTe/CdHgTe double quantum well heterostructures and its application for reversible change in the conductivity type

Abstract

We report a detailed study of the bipolar persistent photoconductivity in an HgTe/CdHgTe double quantum well (DQW), which can be a perspective for studying topological states in these structures. Photoconductivity spectra measurements in the range of 1.1–3.1 eV as well as transport measurements under different illumination conditions were performed at T = 4.2 K. Based on the results, the processes occurring in the structure under illumination and leading to a change in the carrier concentration in the DQW have been established. They include interband generation in the CdTe cap layer and in the CdHgTe barrier layer and electron transitions from the spin-split band in the CdHgTe barrier layer to the conduction band in the CdTe cap layer. The presence of the CdTe cap layer and the appropriate cadmium fraction in the CdHgTe barrier layers have been shown to be the main factors determining the key features of the spectra. Finally, we suggest an effective method of controlling the conductivity type of HgTe/CdHgTe structures using light with different wavelengths.

Актуальные Проблемы Физики Полупроводников: Наноструктуры, Эпитаксия, Фотоника И Электроника. Научные Результаты ИФП СО РАН За 2022 Год

“…Сопоставление поведения контраста от напряжения на этой границе и на морфологической ступени, на которой контраст не зависит от напряжения на туннельном промежутке, показано на Рис. 109. Сделан вывод, что контраст имеет не морфологическое происхождение, а связан с различием плотности состояний этих структур.…”

Cap Layer Effect on Key Features of Persistent Photoconductivity Spectra in HgTe/CdHgTe Double Quantum Well Heterostructures

“…In this respect, HgTe/CdHgTe heterostructures with DQWs look like very suitable objects for research. They demonstrate not only an ability to decrease or increase the carrier concentration after illumination, but also the possibility of a reversible change in the conductivity type [16].…”

“…This effect is often used as an effective and simple method for controlling the concentration of charge carriers. PPC can be observed both in bulk semiconductors [1][2][3][4] and in lowdimensional structures [5][6][7][8][9][10][11][12][13][14][15][16]. In most cases, positive PPC takes place, which means that the carrier concentration (and, accordingly, conductivity) increases when the illumination is turned on.…”

“…This type of PPC is called bipolar and has the most practical interest. Bipolar PPC has been observed in, for example, InAs/AlSb heterostructures [11][12][13] and HgTe/CdHgTe heterostructures [14][15][16].…”

“…To date, PPC in HgTe/CdHgTe heterostructures with DQWs has been studied in detail only in [15,16]. In these two papers, the presence of the bipolar PPC was demonstrated, the main features of the PPC spectra were detected, and the main reasons for their appearance were identified.…”