J.F. Butler

LONG‐WAVELENGTH INFRARED Pb1−xSnxTe DIODE LASERS

Diode lasers with emission wavelengths as long as 28 μ have been fabricated using Pb1−xSnxTe with x up to 0.27. Properties of laser diodes at 77°K and 12°K have been measured for a number of compositions in the range 0.15 ≤ x ≤ 0.27. The vapor growth and annealing‐diffusion steps were performed in a special quartz ampoule which remained sealed throughout the process. Threshold current densities were dependent on diode surface conditions and could be reduced by at least 50% by etching.

DIODE LASERS OF Pb1−ySnySe AND Pb1−xSnxTe

Infrared laser emission at a number of wavelengths between 9.4 μ and 13.7 μ has been obtained from diodes of Pb1−ySnySe and Pb1−xSnxTe at 12°K and 77°K. Diodes were fabricated from vapor‐grown Pb1−ySnySe and both vapor‐grown and Bridgman‐grown Pb1−xSnxTe. Emission data indicate that, as in Pb1−xSnxTe, the energy gap in Pb1−ySnySe decreases with increasing Sn concentration, becoming zero at 12°K for some value of y within the range 0.11 ≤ y ≤ 0.14.

Magnetoemission experiments in Pb1−cSnxTe☆

Abstract Reduced effective masses and g -factor magnitudes inPb 1−x Sn x Te (0 ≤ x ≤0.27) are deduced from the dependence of the emission spectra on magnetic fields. Their band gap dependence is as expected if valence-conduction band interaction provides the primary contribution, with higher and lower lying bands having a lesser, but significant, effect.

Bismuth-doped Pb 1-x Sn x Te diode lasers with low-threshold currents

Diode lasers have been fabricated from Bi-doped Pb 1-x Sn x Te with 0.24 \leq x \leq 0.27 , which have threshold current densities as low as 1400 A.cm-2at 77°K and 71 A.cm-2at 12°K, whereas diodes fabricated from undoped Pb 1-x Sn x Te> in this composition range did not exhibit laser action for current densities up to 30 000 A.cm-2at 77°K and had threshold current densities greater than 200 A.cm-2at 12°K. Bi doping also results in a reduction in the annealing times required to form suitable p-n junctions from several weeks to a few days. These effects can be tentatively related to an increased electron concentration in the n -type layer due to the addition of Bi, a donor impurity. A curve of Eg versus x for 0 \leq x \leq 0.4 , which agrees with predictions, is presented.

Properties of the PbSe diode laser

Diode laser action has been obtained at 8.5μ with PbSe. This laser is of potential interest for terrestrial communications since its emission is in the 8-to-14-μ atmospheric window, a spectral region of high atmospheric transparency where attenuation due to scattering by haze is low. Fabrication techniques are described which are based on controlling carrier type and concentration by adjusting the Pb:Se ratio. Below threshold for laser action, the emission exhibits two spectral peaks, one near 8.5μ which increases superlinearly with current and another near 10.1μ which increases slowly with current. Laser action associated with the 8.5μ peak is observed above a threshold Current density of 2000 A cm-2. From measurements which did not resolve the cavity mode structure, the emission peak was found to shift to higher energies in a [100] oriented magnetic field at the rate of 7.1 \times 10^{-8} eV per gauss, or 17 Mc/s per gauss. This is the expected shift if the emission is associated with band-to-band transitions. The threshold current decreased to a fraction of its zero field value in a magnetic field of approximately 10 kilogauss, then increased slowly with higher fields.

PbSe diode laser

Laser action at 8.5 µ has been observed from PbSe diodes. The diodes were prepared from p-type PbSe Which had been annealed under closely controlled conditions of temperature and Se vapor pressure to obtain a hole concentration of 4.7 \times 10^{17} cm-3. The n-p junction was formed by diffusing excess Pb into a cleaved