Data are presented showing that Zn diffusion into an AlAs‐GaAs superlattice (41 Lz∼45‐A GaAs layers, 40 LB∼150‐A AlAs layers), or into AlxGa1−xAs‐GaAs quantum‐well heterostructures, increases the Al‐Ga interdiffusion at the heterointerfaces and creates, even at low temperature (<600 °C), uniform compositionally disordered AlxGa1−xAs. For the case of the superlattice, the diffusion‐induced disordering causes a change from direct‐gap AlAs‐GaAs (Eg∼1.61 eV) to indirect‐gap AlxGa1−xAs (x∼0.77, EgX∼2.08 eV).

Disorder of an AlAs‐GaAs superlattice by impurity diffusion

An overview is given of the direct modulation performance of high-speed semiconductor lasers. The high-speed response characteristics are described using a cascaded two-port model of the laser. This model separates the electrical parasitics from the intrinsic laser and enables these subsections to be considered separately. The presentation concentrates on the small-signal intensity modulation and frequency modulation responses, and the large-signal switching transients and chirping. Device-dependent limitations on high-speed performance are explored and circuit modeling techniques are briefly reviewed.

High-speed modulation of semiconductor lasers

Room‐temperature cw operation has been achieved for stripe‐geometry double‐heterostructure Ga0.12In0.88As0.23P0.77/InP diode lasers emitting at 1.1 μm. The heterostructures were grown by liquid‐phase epitaxy on melt‐grown InP substrates, and stripes were defined by using proton bombardment to produce high‐resistance current‐confining regions.

Room‐temperature cw operation of GaInAsP/InP double‐heterostructure diode lasers emitting at 1.1 μ m

We report on electrically driven amplified spontaneous emission and lasing in tetracene single crystals using field-effect electrodes for efficient electron and hole injection. For laser action, feedback is provided by reflections at the cleaved edges of the crystal resulting in a Fabry-Perot resonator. Increasing the injected current density above a certain threshold value results in the decreasing of the spectral width of the emission from 120 millielectron volts to less than 1 millielectron volt because of gain narrowing and eventually laser action. High electron and hole mobilities as well as balanced charge carrier injection lead to improved exciton generation in these gate-controlled devices. Moreover, the effect of charge-induced absorption is substantially reduced in high-quality single crystals compared with amorphous organic materials.

https://science.sciencemag.org/content/sci/289/5479/599.full.pdf

An organic solid state injection laser.

The high-frequency modulation characteristics of InGaAsP ridge waveguide lasers at 1.55 μm and etched mesa buried heterostructure (EMBH) lasers at 1.3 μm are investigated. Small-signal and large-signal circuit models are developed for both devices, and the main factors which influence the high-frequency modulation response are established. It is shown that the electrical parasitics in the chip dominate the small-signal frequency response of the EMBH laser and limit the large-signal turn-on and turn-off times. The small-signal and large-signal responses of both devices show strong damping of the relaxation oscillations. This damping can be modeled accurately using field-dependent optical gain compression in the rate equations.

High-frequency characteristics of directly modulated InGaAsP ridge waveguide and buried heterostructure lasers

The fabrication procedure, electrical properties, optical-bean characteristics, spectral characteristics, and temperature dependence of emission wavelength and threshold of InGaAsP buried-heterostructure (BH) lasers emitting at 1.3 μm are described. The dimensional requirements for fundamental-transverse mode operation have been determined. BH devices are characterized by low threshold currents, fundamental transverse mode operation, linear light output, and narrow spectral width. For 380 μm long devices threshold currents of 40 mA, slope efficiencies of 18 percent, forward resistance of 5 Ω, and T 0 values of 75 K have been attained.

CW electrooptical properties of InGaAsP(&#955; = 1.3 &#181;m) buried-heterostructure lasers

Pulsed room‐temperature operation of LPE In1−xGaxP1−zAsz double heterojunction (DH) laser diodes at short wavelength is described (Jth≲2×104 A/cm2, λ∼6470 A, heterobarrier ΔE∼137 meV). The differential quantum efficiency of these diodes is ηext∼5%, and is considered to be low because of large diode size, thick active region, probably some layer mismatch and growth defects, and relatively poor heat sinking. The temperature dependence of threshold current density (Jth∼J0 expT/T0, T0∼74 °K) is presented in the range 77–300 °K and is compared with similar diodes having smaller heterobarriers and which, as expected, exhibit poorer performance (smaller T0).

Pulsed room‐temperature operation of In1−xGaxP1−zAsz double heterojunction lasers at high energy (6470 Å, 1.916 eV)

Liquid phase epitaxial (LPE) In1−x′Gax′P1−z′ Asz′/In1−xGaxP1−zAsz/In1− x′ Gax′P1−z′Asz′ (x′∼0.66, z′∼0.005; x∼0.71, z∼0.10) double‐heterojunction laser diodes that operate in the yellow at relatively low current densities (J<104 A/cm2, λ∼5850 A, 77 °K) are reported. The lattice‐matched LPE quaternary growth process, employing GaAs1−yPy substrates, and the double‐heterojunction laser diode properties are described.

Low‐threshold LPE In1−x′Gax′P1−z′ Asz′/In1−xGaxP1−zAsz/In1− x′ Gax′P1−z′Asz′ yellow double‐heterojunction laser diodes (J<104 A/cm2, λ∼5850 Å, 77 °K)

Improved yellow‐spectrum double‐heterojunction In1−xGaxP1−zAsz laser diodes constructed by LPE on VPE GaAs1−yPy substrates are described. The lattice‐matched LPE quaternary alloy growth process is outlined, as well as the need for complete melt removal between the growth of each heterojunction layer, which is more difficult for In‐rich melts than for Ga‐rich melts when lattice match is a problem. Over two times lower threshold current densities are demonstrated (Jth?3.6×103 A/cm2, λ?5920 A, 77 °K) than for the first reported diodes of this type. The temperature dependence of laser threshold current density is presented in the range 4.2–200 °K. The threshold current density can be approximated as Jth∝exp(T/T0) with T0?52 °K in the range 50–175 °K, which compares well with red‐orange AlGaAs double heterojunctions (T0?42 °K) having greater heterobarriers. Laser operation in the yellow‐orange portion of the visible spectrum at ∼200 °K is demonstrated. These results on thick (1.5 μm) active layer diodes, havin...

Yellow In1−xGaxP1−zAsz double‐heterojunction lasers

Multiple liquid phase epitaxy of In1−xGaxP1−z Asz‐InP double heterojunctions, from a single set of In‐rich melts, is demonstrated, and is shown to be a useful technique for the study of the problem of lattice matching at heterojunction interfaces and for growing large numbers of low‐threshold (’’defect‐free’’) DH laser wafers (λ∼1 μm).

P. D. Wright

Papers

CW electrooptical properties of InGaAsP(λ = 1.3 µm) buried-heterostructure lasers

Pulsed room‐temperature operation of In1−xGaxP1−zAsz double heterojunction lasers at high energy (6470 Å, 1.916 eV)

Low‐threshold LPE In1−x′Gax′P1−z′ Asz′/In1−xGaxP1−zAsz/In1− x′ Gax′P1−z′Asz′ yellow double‐heterojunction laser diodes (J<104 A/cm2, λ∼5850 Å, 77 °K)

Yellow In1−xGaxP1−zAsz double‐heterojunction lasers

Multiple liquid phase epitaxy of In1−xGaxP1−zAsz double‐heterojunction lasers: The problem of lattice matching

P. D. Wright

Papers

CW electrooptical properties of InGaAsP(&#955; = 1.3 &#181;m) buried-heterostructure lasers

Pulsed room‐temperature operation of In1−xGaxP1−zAsz double heterojunction lasers at high energy (6470 Å, 1.916 eV)

Low‐threshold LPE In1−x′Gax′P1−z′ Asz′/In1−xGaxP1−zAsz/In1− x′ Gax′P1−z′Asz′ yellow double‐heterojunction laser diodes (J<104 A/cm2, λ∼5850 Å, 77 °K)

Yellow In1−xGaxP1−zAsz double‐heterojunction lasers

Multiple liquid phase epitaxy of In1−xGaxP1−zAsz double‐heterojunction lasers: The problem of lattice matching

CW electrooptical properties of InGaAsP(λ = 1.3 µm) buried-heterostructure lasers