R. F. Leheny

DIRECT DETERMINATION OF OPTICAL GAIN IN SEMICONDUCTOR CRYSTALS

We report a new technique for measuring the stimulated emission spectrum and optical gain of semiconductor materials. Amplified spontaneous emission is used to determine the gain factor by relating the measured variation in light output to variation in the length of the excitation beam. Results for CdS crystals at 2°K are presented that indicate net gains as high as 160 cm−1 at λ = 4907 A are possible with ∼ 12‐MW/cm2 optical pump power density from a nitrogen laser.

Optical gain in semiconductors

Abstract Direct measurements of optical gain in semiconductors give information on the stimulated recombination process that cannot be easily obtained from an oscillating semiconductor laser. The effects of various material parameters on the gain and saturation factors can be easily studied. The temperature dependence of the stimulated recombination in high purity GaAs will be presented as an example. The pertinence of the gain and saturation factors to the threshold and efficiency of semiconductors laser oscillators will be discussed. The significance of gain measurements on GaP doped with isoelectronic traps will be considered in terms of the observed gain and saturation properties.

Stimulated Emission and Laser Action in Gallium Nitride

Stimulated emission and laser action have been observed near 3.45 eV in single‐crystal needles of GaN. These observations support the earlier suggestion that GaN is a direct band‐gap semiconductor with Eg∼3.50 eV at 2°K. Furthermore, the occurrence of very high gain (g∼105 cm−1) in the stimulated emission emphasizes the possible device potential of this material.

Dynamics of hot carrier cooling in photo-excited GaAs

Abstract Carrier relaxation following excitation with subpicosecond optical pulses, determined from time resolved nearband gap transmission spectrum changes, is described for GaAs. For n

Dynamic Burstein shift in GaAs

Abstract We present our results on the saturation of interband optical absorption in GaAs obtained by using a tunable i.r. dye laser as the excitation source. We show that a quantitative fit to the data can be obtained if we include the effects of bandgap renormalization and carrier heating in the model.

Velocity field characteristics of minority carriers (electrons) in p‐In0.53Ga0.47As

Steady‐state velocity field characteristics for photoexcited minority electrons in p‐In0.53Ga0.47As are reported. A low‐field drift mobility of 6000 cm2/V s for ∼1017 cm−3 impurities and a high‐field drift velocity of 2.6×107 cm/s at 7.5 kv/cm are found. There is no evidence of transferred electron effects, a result which we attribute to energy scattering by holes and which leads to an enhancement of electron drift velocity.

Compositional dependence of the electron mobility in Inl-x Gax Asy P1-y

Hall mobility measurements for the alloy III–V quaternary material In1-x}Gax}Asy}P1-y} lattice matched to semi-insulating InP substrates are described. For samples spanning the entire compositional range, the carrier concentration varied from 0.4x1016} to 1017}cm−3 and the room temperature mobilities varied from 3800cm2}/Vsec up to 11,000cm2}/Vsec. Temperature variation of the mobility in the range from 80K to 300K was investigated for selected samples. The results demonstrate that disorder scattering makes a significant contribution to limiting the mobility for material spanning the midrange (y∼0.5).

An In 0.53 Ga 0.47 As junction field-effect transistor

Preliminary results are reported for the operation of a junction field-effect transistor fabricated from In<inf>0.53</inf>Ga<inf>0.47</inf>As grown lattice-matched to an InP:Fe substrate.

Optical Gain in Lightly Doped GaAs

Measurements of both small‐signal gain and stimulated emission spectra for optically pumped GaAs are described. Saturation of the amplification process is shown to play an important role in determining the spectral distribution of the stimulated emission. These measurements indicate that intrinsic gain in high‐purity material does not result from band‐to‐band recombination and in its place an interpretation in terms of free‐exciton radiative Auger recombination is suggested.

Hot‐carrier effects in 1.3‐μ In1−xGaxAsyP1−y light emitting diodes

We report the first observation of carrier heating effects for In1−xGaxAsyP1−y 1.3‐μ light emitting diodes, including variation of carrier temperature with injection current and ambient temperature. These results demonstrate that carrier temperature reaches 400 K at 2.5×104 A/cm2 (260 mA) for an LED with room‐temperature ambient. Such significant heating must be taken into account in modeling device performance.