Terahertz Electroluminescence of Shallow Impurities in AlGaN/GaN Heterostructures at Temperatures above 80 K

In this work terahertz (THz) electroluminescence of shallow impurities in AlGaN/GaN high electron mobility transitor (HEMT) structures are studied at temperatures above 80 K. The samples are excited with electric field pulses of up to 300 V cm−1 and duration of τp=1.6  ms. The THz emission spectra are measured in vacuumed environment by means of infrared Fourier transform spectroscopy. Resonant 1s − 2p electron transitions in energy levels of residual oxygen and silicon impurities are observed at temperatures above 80 K. A comparison of the area under the shallow impurities electroluminescence signal correlates with the growth conditions of the AlGaN/GaN heterostructures. In such a way a method to monitor the ratio between ionized shallow impurities in unintentionally doped AlGaN/GaN HEMT structures in the THz frequency range is proposed. In addition, the resonant electroluminescence signals are found intermixed with the THz emission caused by the hot electron transitions from conduction band to shallow donors as well as the black‐body radiation of heated AlGaN/GaN HEMT channel. It is found that the temperature increase of the conductive channel greatly suppressed the electroluminescence signal. Therefore, a proper cooling of the sample should be provided in advance.

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