The blue-shift effect of the ion-milling-formed HgCdTe photodiodes

Abstract

Ion milling-formed n-on-p diodes of HgCdTe were studied by photoluminescence spectroscopy. A sequence of spectra measured across a square junction show that the luminescence peaks of the ion-eroded region shifted strongly to shorter wavelength than those defined by monolithic material. This shift may be well interpreted in terms of Burstein-Moss (BM) effect and is important to device fabrication.

Photoluminescence in Mercury Cadmium Telluride – a Historical Retrospective. Part II: 2004–2022

“…A blue-shift of the PL peak immediately after ion etching with subsequent red-shift upon relaxation discussed above [26,27,32] (see also Ref. [72] by Pociask et al), was observed and explained by the BM effect associated with formation of donor complexes involving interstitial mercury atoms HgI released during the etching, and disintegration of the complexes with time.…”

“…Therefore, the rest of the shift (29 meV) was attributed to the BM effect, with calculations of the Fermi level shift as a result of heavy electron doping confirming its exact value. The authors of this review would like to note, though, that the shift observed by Zha et al [26,27] should not be, in fact, permanent, as electron concentration in ion-milling-induced n-type material is prone to relaxation and gradually decreases with time [29,31].…”

“…Modulated PL spectroscopy with a step-scan FTIR spectrometer was used for the study of the so-called blue-shift in PL and photoconductivity (PC) spectra of the n-on-p MCT photodiodes fabricated with ion milling [26,27]. Ion milling or ion (plasma) etching are used in MCT technology for fabrication of n-on-p photodiode structures, as lowenergy (1 to 5 keV) ion or plasma treatment causes controllable p-to-n conductivity type conversion in p-type material [28,29].…”

“…Ion milling or ion (plasma) etching are used in MCT technology for fabrication of n-on-p photodiode structures, as lowenergy (1 to 5 keV) ion or plasma treatment causes controllable p-to-n conductivity type conversion in p-type material [28,29]. Zha et al [26,27] reported that a sequence of PL spectra measured across a square p-n junction fabricated with ion milling showed luminescence peaks of the milled area shifting strongly to shorter wavelengths in comparison to the spectra of the initial LPE-grown p-type material. This blue-shift could not be attributed to the composition non-uniformity of the material, as the value of the shift was ~39 meV and was much larger than the non-uniformity-related energy uncertainty of ~6 meV as revealed by PL measurements performed at different spots of the sample.…”

“…This blue-shift could not be attributed to the composition non-uniformity of the material, as the value of the shift was ~39 meV and was much larger than the non-uniformity-related energy uncertainty of ~6 meV as revealed by PL measurements performed at different spots of the sample. The shift was interpreted in terms of Burstein-Moss (BM) effect, as electron concentration in the milled area (assessed as n ≈ 7.2×10 16 cm -3 ), according to Zha et al [27], exceeded threshold concentration of n-region for the occurrence of the effect (which was estimated to be n ≈ 8×10 15 cm -3 for T = 77 K and Eg = 0.197 eV). To explain the exact value of the shift, it was noted that a red-shift of the absorption peak was previously found for p-type MCT with VHg acting as acceptors [30].…”