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Gallium nitride (GaN) films grown by hydride vapor phase epitaxy on a variety of substrates have been investigated to study what role silicon and oxygen impurities play in determining the residual donor levels found in these films. Secondary ion mass spectroscopy analysis has been performed on these films and impurity levels have been normalized to ion implanted calibration standards. While oxygen appears to be a predominate impurity in all of the films, in many of them the sum of silicon and oxygen levels is insufficient to account for the donor concentration determined by Hall measurements. This suggests that either another impurity or a native defect is at least partly responsible for the autodoping of GaN. Additionally, the variation of impurity and carrier concentration with surface orientation and/or nucleation density suggests either a crystallographic or defect-related incorporation mechanism.

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unpublished). 6 This formalism for the natural-mode E e field parallels that given by Stix in the approximate theory [Ref.The temperature dependence of laser emission in Pb^^Sn^Se diodes in the composition range 0 ^x ^0.3 has recently been reported 1 and the magnetic field dependence of laser emission and spontaneous luminescence has been measured for PbS, PbSe, and PbTe 2 and for low-SnTe-content Pb^^Sn^Te diodes. 3 We report here the results of measurements made on a number of Pbi-^Sn^Se diode lasers in the above composition range at magnetic fields up to 145 kG. The results support the model previously proposed 4 in which the valence-and conduction-band states in Pb^^Sn^Se alloys approach each other, invert, and move apart as SnSe is added to PbSe. At low temperatures this inversion occurs at about x = 0.15. For the alloys on the SnSe-rich side of the inversion point the lowest energy transition between magnetic levels of the conduction and valence bands has an energy which decreases with increasing magnetic field. To our knowledge this is the first such observation in any material. In addition the results give a direct indication of the effect that the higher lying energy bands have on the conduction and valenceband-edge masses and ^factors in these materials. 4, Sec. 5-4, in which T = kpJ i (vp)K 1 '(kp)-ppJ 1 '(vp)K 1 (kp)]. 7For the magnetic-field measurements the diodes were near liquid-He temperature and oriented with the diode current parallel to the magnetic field in a (100) crystallographic direction. The laser radiation was emitted perpendicular to this direction. The photon energy of the laser emission as a function of magnetic field is shown in Fig. 1 for diodes of Pb^^Sn^Se with x = 0, 0.05, and 0.10 and in Fig. 2 for # = 0.19, 0.22, and 0.28. The Landau levels shown schematically in the insets identify the transitions observed. At low magnetic fields one generally observes the line T 2 . As the field is increased the emission switches to T v If the diode current is increased the T 2 emission persists up to higher magnetic field values and in some cases a third line T 3 is observed. For all of the alloys studied with #<0.15 (including PbSe) the T\ line is found to have a positive slope, in most cases about 10 ~7 eV/G. For alloys with x > 0.15 the slope of this line is negative but has about the same magnitude. The zero-field energy gap as a function of alloy composition is shown in Fig. 3. The mole fraction of SnSe (x) was measured using an electron microprobe, and the energy-gap values were obtained from extrapolations of the magnet- MAGNETIC FIELD DEPENDENCE OF LASER EMISSION IN Pb x ^Sn^Se DIODES*The magnetic field dependence of long-wavelength infared laser emission has been studied in Pb^^Sn^Se diodes for compositions in the range 0 ^x ^0.3. For x >0.15 the energy of the lowest transition decreases with increasing magnetic field whereas for x <0.15 this energy increases. This unique observation is consistent with a theory of magnetic energy levels proposed by Baraff and also strongly supports...

Light scattering by edge dislocations and the resulting loss coefficient have been modeled for GaN layers. Phase-front deformation caused by the refractive-index variation in the dislocation’s strain field has been considered and the resulting scattering loss calculated. We show that the high dislocation densities observed in recent GaN layers can result in significant large loss coefficients. The present work also offers some insights for improved lasers.

Avalanche photodiodes have been demonstrated utilizing GaN grown by hydride vapor-phase epitaxy. Spatially uniform gain regions were achieved in devices fabricated on low-defect-density GaN layers that exhibit no microplasma behavior. A uniform multiplication gain up to 10 has been measured in the 320–360 nm wavelength range. The external quantum efficiency at unity gain is measured to be 35%. The electric field in the avalanche region has been determined from high-voltage C–V measurements to be ∼1.6 MV/cm at the onset of the multiplication gain. Electric fields as high as 4 MV/cm have been measured in these devices. Response times are found to be less than 5 μs, limited by the measurement system.

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