The physics of the growth mechanisms, characterization of epitaxial structures and device properties of GaAs and other compound semiconductors on Si are reviewed in this paper. The nontrivial problems associated with the heteroepitaxial growth schemes and methods that are generally applied in the growth of lattice mismatched and polar on nonpolar material systems are described in detail. The properties of devices fabricated in GaAs and other compound semiconductors grown on Si substrates are discussed in comparison with those grown on GaAs substrates. The advantages of GaAs and other compound semiconductors on Si, namely, the low cost, superior mechanical strength, and thermal conductivity, increased wafer area, and the possibility of monolithic integration of electronic and optical devices are also discussed.

Gallium arsenide and other compound semiconductors on silicon

Recent advances in epitaxial growth have led to the prospect of artificial modification of the electronic structure or band structure of semiconductor materials. The combination of strain and quantum confinement in the valence band can lead to substantially more favorable energy dispersion relations for laser action than those existing in the natural semiconductor crystal. Numerical results are presented for a series of alloy compositions with a bandgap near the 1.55- mu m optimum wavelength for optical communications. The laser threshold current and the intervalence band absorption can be significantly diminished in properly engineered band structures. >

Band structure engineering of semiconductor lasers for optical communications

Theory and experiments of single-mode ridge waveguide GaAs-AlGaAs semiconductor ring lasers are presented. The lasers are found to operate bidirectionally up to twice the threshold, where unidirectional operation starts. Bidirectional operation reveals that just above threshold, the lasers operate in a regime where the two counterpropagating modes are continuous wave. As the injected current is increased, a new regime appears where the intensities of the two counterpropagating modes undergo alternate sinusoidal oscillations with frequency in the tens of megahertz range. The regime with alternate oscillations was previously observed in ring lasers of the gas and dye type, and it is here reported and investigated in semiconductor ring lasers. A theoretical model based on a mean field approach for the two counterpropagating modes is proposed to study the semiconductor ring laser dynamics. Numerical results are in agreement with the regime sequence experimentally observed when the injected current is increased (i.e., bidirectional continuous-wave, bidirectional with alternate oscillations, unidirectional). The boundaries of the different regimes are studied as a function of the relevant parameters, which turn out to be the pump current and the conservative and dissipative scattering coefficients, responsible for an explicit linear coupling between the two counterpropagating field modes. By a fitting procedure, we obtain good numerical agreement between experiment and theory, and also an estimation for the otherwise unknown scattering parameters.

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Operating regimes of GaAs-AlGaAs semiconductor ring lasers: experiment and model

Lasing characteristics of strained quantum well (QW) structures such as InGaAs/AlGaAs on GaAs and InGaAs/InAlAs on InP were analyzed by taking into account the band mixing effect in the valence band. A relaxation oscillation frequency fr, which gives a measure of the upper modulation frequency limit, was found increased three times in a 50 A In0.9Ga0.1As/In0.52Al0.48As QW structure compared with that in a 50 A GaAs/Al0.4Ga0.6As QW structure for the undoped case. One of the main factors for this improved frequency bandwidth is attributed to the reduced subband nonparabolicity as well as the reduced valence‐band density of state in the strained QW structure. The corresponding lasing threshold current is one order of magnitude smaller than that of the GaAs/AlGaAs QW structure. With a p doping in the QW the fr value increases, and the 3 dB cutoff frequency of about 90 GHz will be expected with an acceptor concentration of 5×1018 cm−3 in the In0.9Ga0.1As/In0.52Al0.48As QW.

Extremely wide modulation bandwidth in a low threshold current strained quantum well laser

The present disclosure relates to a semiconductor light-emitting element, which comprises: a first light-emitting part, a second light-emitting part, and a third light-emitting part, wherein each of the light-emitting parts includes multiple semiconductor layers including a first semiconductor layer, an active layer, and a second semiconductor layer, laminated in sequence, the first semiconductor layer having a first conductivity, the active layer generating light through the recombination of an electron and a hole, and the second semiconductor layer having a second conductivity different from the first conductivity; a non-conductive reflecting film which is formed to cover the multiple semiconductor layers and reflects light generated from the active layer; a first electrode which is provided to electrically communicate with the first semiconductor layer of the first light-emitting part and which supplies one of an electron and a hole; a second electrode which is provided to electrically communicate with the second semiconductor layer of the second light-emitting part and which supplies the other of the electron and the hole; and an auxiliary pad formed on the non-conductive reflecting film which covers the third light-emitting part.

Semiconductor light emitting element

Light‐emitting diodes have been fabricated in GaAs grown by metalorganic chemical vapor deposition on vapor‐deposited epitaxial Ge films on Si substrates. The light‐emitting junction was formed by zinc diffusion into the n‐type GaAs layer. Room‐temperature light emission centered at 872 nm has been observed.

GaAs light‐emitting diodes fabricated on Ge‐coated Si substrates

Ridge waveguide lasers emitting near 1 μm have been made on a GaAs substrate using a single GaInAs strained‐layer quantum well in a GaAs/AlGaAs graded‐index separate confinement heterostructure. The epitaxial layers were grown by low‐pressure metalorganic chemical vapor deposition, and the ridge waveguide was fabricated by chemically assisted ion beam etching. The lasers have threshold currents near 17 mA with fundamental lateral mode operation to five times this value. These are the first reported strained‐layer current‐injection lasers to run cw at room temperature; they operate, without bonding, to greater than 24 mW/facet (100 mA dc), and have 18 mW/facet (80 mA dc) lifetimes in excess of 144 h.

Ridge waveguide injection laser with a GaInAs strained‐layer quantum well (λ=1 μm)

Pseudomorphic InGaAs lasers with cw operating lifetimes exceeding 5000 h are reported for the first time. The device structure, grown by low‐pressure metalorganic chemical vapor deposition, incorporates a single In0.37Ga0.63As strained‐layer quantum well in a GaAs/AlGaAs graded‐index separate confinement heterostructure. These devices are remarkable for their immunity to sudden failure and for their (gradual) degradation rates which are comparable to the best GaAs lasers.

Long‐lived InGaAs quantum well lasers

A method of providing asymmetric feedback in the triangular ring laser structure was devised through the simple alterations of the waveguide shape. Two kinds of alterations were designed and implemented, one being the “optical diode,” the other being the tapered waveguide. Unidirectional operation was achieved for the ring lasers, with a single-beam slope efficiency of 0.23 W/A, which was the highest single-beam slope efficiency reported for semiconductor ring lasers.

Unidirectional operation of waveguide diode ring lasers

A monolithic optoelectronic circuit, consisting of a GaAs light‐emitting diode (LED) driven by a Si metal‐oxide‐semiconductor (MOS) transistor, has been fabricated. Light output as a function of applied gate voltage was measured. The LED’s were fabricated in GaAs layers on Ge‐coated Si substrates containing MOS transistors. Normal transistor performance was observed after the GaAs LED fabrication, indicating that GaAs and Si processing technologies appear to be compatible.

Joseph M. Ballantyne

Papers

GaAs light‐emitting diodes fabricated on Ge‐coated Si substrates

Ridge waveguide injection laser with a GaInAs strained‐layer quantum well (λ=1 μm)

Long‐lived InGaAs quantum well lasers

Unidirectional operation of waveguide diode ring lasers

Monolithic integration of GaAs light-emitting diodes and Si metal-oxide-semiconductor field-effect transistors