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0Photo- and electroluminescence in mid-infrared range from HgCdTe based waveguide structures
S. Morozov1*, V. Rumyantsev1, A. Okomelkov1, V. Utochkin1, M. Fadeev1, K. Mazhukina1, A. Razova1, A. Yantser1, N. Mikhailov2, S. Dvoretskii2, V. Varavin2, S. Kraev1, E. Arkhipova1, V. Gavrilenko1
1-Institute of Microstructure Physics RAS, Nizhny Novgorod, 603087, Russia 2- Institute of Semiconductor Physics RAS, Novosibirsk, 630090, Russia
* more@ipmras.ru
Currently, the development of semiconductor emitters in the mid-infrared range (IR) is one of the priority tasks in applied physics. Heterostructures with HgCdTe/CdHgTe quantum wells (QWs) offer a number of unique properties for interband lasers in the mid-IR and THz ranges. In particular, "threshold" Auger recombination can be significantly reduced for a given energy of interband transitions. Stimulated emission under optical pumping of HgCdTe heterostructures (MCT) at wavelengths from 2.5 to 31 p,m was reported in [1]. However, current pumping is preferred for a semiconductor emitter, while it is difficult to obtain p-type MCT materials. Group I elements diffuse very easily outside the doping region during growth and Group V elements require additional annealing for dopants to be incorporated in Te sites rather than that of Cd or Hg. This work investigates an alternative method of current pumping: impact ionization in a strong electric field. Nonequilibrium degenerate distribution of charge carriers is expected to provide amplification via interband transitions without forming a p-n junction.
Structure under study were grown by molecular beam epitaxy on semi-insulating GaAs (013) substrates with ZnTe and CdTe buffers. The active region contained a number of QW or a bulk HgCdTe with a cadmium content of ~21% (Table 1). To carry out current pumping, two rectangular multilayer Ti/Mo/Au contacts with corresponding thicknesses of 20/30/100 nm were deposited onto the surface of the sample. The gap between the lateral stripe contacts was either 200 or 500 p,m. Copper or silver wire was soldered to the contacts through indium solder.
Table 1. Parameters and characteristics of structures.
xCd is the fraction of Cd in the active layer, d is the thickness of the QW, N - number of QWs, Dclad is the thickness of the
upper cladding waveguide layer, Ebr is the electric field strength of the breakdown, Edm is the electric field at which irreversible degradation of the structure occurs, W is the energy in the current pulse during electric Edm field.
Fig. 1. Electroluminescence spectra of sample Q14 at different electric fields.
# XCd dxN, nm Dclad, nm Ebr, V/cm Edm, kV/cm W, mJ
B1 0.21 5000 100 300 1 3000
Q14 0.33 95 500 1200 2 50
Q15 0.02 3.2x5 750 1200 1.5 220
Q21 0.06 2.8x15 300 6000 10 120
All four samples provided both photo- and electroluminescence accompanied by a superlinear current-voltage characteristic. However, only spontaneous emission was observed. Comparison with theoretical estimations [2] indicate that lasing requires higher electric field, which entails contact area degradation. The ways to refine the contact for stable operation at high electric fields are discussed.
The research was carried out within the state assignment of Ministry of Science and Higher Education of the Russian Federation (theme No. 124050300055-9 (FFUF-2024-0045)).
[1] S.V. Morozov, et al, ACS Photonics, Vol. 8, No. 12, 3526-3535, (2021).
[2] A.A. Dubinov, Journal of Luminescence 263, 120066, (2023).
