Abstract Generated abstract
This study examines whether a GaSe single crystal can serve as the active medium for an optical quantum generator excited by fast electrons. The authors irradiated p-type GaSe crystals cooled to liquid nitrogen temperature with 200 keV electron pulses and recorded the luminescence spectrum, focusing on the strongest emission near 5925 Å. The spectrum extended from 5870 to 6150 Å with four maxima, and increasing excitation current narrowed the 5925 Å line, while higher current also shifted it to longer wavelengths, likely because of crystal heating. Silvering the crystal surfaces produced further line narrowing and additional narrow emission lines at 5960 and 5983 Å, suggesting conditions favorable for induced radiation in GaSe under electron-beam excitation.
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PHYSICS
Corresponding Member of the Academy of Sciences of the USSR N. G. BASOV, O. V. BOGDANKEVICH,
A. N. PECHENOV, G. B. ABDULAEV, G. A. AKHUNDOV, E. Yu. SALAEV
INDUCED RADIATION IN A GaSe SINGLE CRYSTAL UNDER EXCITATION BY FAST ELECTRONS
In order to determine the possibility of creating an optical quantum generator (OQG), excited by a beam of fast electrons, on semiconductors of the type $A^{III}B^{VI}$, we chose a GaSe single crystal, whose luminescence under such excitation had not been investigated.
The obtaining of an OQG with electron pumping in a CdS crystal was reported in ($^{1,2}$). To study the action of fast electrons, $p$-GaSe crystals were used, which were obtained by the method described in ($^3$) and had an equilibrium carrier concentration of $5 \cdot 10^{15}\ \text{cm}^{-3}$ and a resistivity of $\sim 200\ \Omega \cdot \text{cm}$ at $300^\circ\text{K}$. Cleaved single-crystal layers had natural plane-parallel mirror faces. Crystals 0.1 mm thick and less were placed on a cold finger in a cryostat and cooled with liquid nitrogen. An electron beam with an energy of about 200 keV and a duration of 2 μsec was directed onto the cleaved surface of the crystal at an angle of $70^\circ$, and the luminescence was observed in a direction perpendicular to the surface. The radiation was recorded on an ISP-51 spectrograph. The emission spectrum is situated in the region from 5870 to 6150 Å, where there are 4 maxima. The maximum intensity lies at a wavelength of 5925 Å, which apparently indicates that the radiation is due to interband recombination. According to ($^4$), the forbidden-band width of GaSe at $77^\circ\text{K}$ is 2.09 eV. The most intense maximum with $\lambda = 5925$ Å was studied on a DFS-12 spectrometer at various values of the current.
Fig. 1. Emission spectrum of GaSe at various values of the electron beam. Currents (arbitrary units): 1—1; 2—4; 3—10.
As is seen from Fig. 1, with increasing density of the exciting current there occurs a narrowing of the 5925 Å line. At larger values of the current (curve 3) a shift of the maximum of this line toward longer wavelengths is observed, which is evidently connected with heating of the crystal.
Silvering of the crystal surfaces leads to an even greater narrowing (almost by a factor of 2) of the 5925 Å line, and in this case additional narrow lines with wavelengths $\lambda$ 5960 and 5983 Å appear.
P. N. Lebedev Physical Institute
Academy of Sciences of the USSR
Institute of Physics
Academy of Sciences of the AzSSR
Received
21 VIII 1964
CITED LITERATURE
- N. G. Basov, O. V. Bogdankevich, A. G. Devyatkov, DAN, 155, 783 (1964).
- N. G. Basov, O. V. Bogdankevich, Congrès international sur la physique des Semiconducteurs, Paris, 1964.
- R. F. Mekhtiev, G. B. Abdulaev, G. A. Akhundov, Dokl. AN AzerbSSR, 18, 11 (1962).
- G. Fischer, Helv. phys. acta, 36, 317 (1963).