Lasers gallium arsenide

Gooch, C.H. Gallium Arsenide Lasers. London Wiley-Intersciene 1969. -Winstel, G.H. Der Halbleiterlaser. In Kleen-Miiller, Laser, p. 360. Berlin-Heidelberg-New York Springer 1969. 

Very broadly speaking, two situations have to be considered in explaining devices such as those we have mentioned. In the first, which is relevant to the ruby laser and to phosphors for fluorescent lights, the light is emitted by an impurity ion in a host lattice. We are concerned here with what is essentially an atomic spectrum modified by the lattice. In the second case, which applies to LEDs and the gallium arsenide laser, the optical properties of the delocalised electrons in the bulk solid are important. 

When the electric field causes conduction electrons to move across the p-/i junction, the resulting situation is one in which the population in the conduction band is greater than the thermal equilibrium population. An excess of electrons in an excited state is an essential feature of lasers, and several semiconductor lasers are based on the p-/i junction. The best known of these is the gallium arsenide laser. 

The gallium arsenide laser actually contains a layer of GaAs sandwiched between layers ofp and /J-type gallium aluminum arsenide (Gai- AfAs). As depicted in Figure 8.12, the band gap of gallium aluminum arsenide is larger than that of gallium arsenide. 

Fig 3. Schematic diagram ol calls gallium arsenide laser... 

Rotating optical disk systems were first demonstrated in the 1960s and paved the way for the Philips Videodisc, introduced in 1973. Less than ten years later, following the successful development of the reliable, low-cost gallium-arsenide laser, the compact disc was launched, leading to the first penetration of laser technology into the consumer market. 

The first semiconductor lasers, fabricated from gallium arsenide material, were formed from a simple junction (called a homojunction because the composition of the material was the same on each side of the junction) between the type and n-ty e materials. Those devices required high electrical current density, which produced damage ia the region of the junction so that the lasers were short-Hved. To reduce this problem, a heterojunction stmcture was developed. This junction is formed by growing a number of layers of different composition epitaxially. This is shown ia Figure 12. There are a number of layers of material having different composition is this ternary alloy system, which may be denoted Al Ga his notation, x is a composition... 

Fig. 12. Details of an aluminum gallium arsenide semiconductor diode laser.

An important development in the 1980s was the multiple stripe laser, capable of emission of high output powers. A number of stripes are placed on a bar perhaps 1 cm wide the output of the different stripes is coupled so that the device may be regarded as a single laser. Bars having continuous output up to 20 W are available in the aluminum gallium arsenide system. A number of bars may then be stacked to form two-dimensional arrays with high values of output power. 

Arsine is used for the preparation of gallium arsenide [1303-00-0] GaAs, (17), and there are numerous patents covering this subject (see Arsenic and ARSENIC alloys). The conversion of a monomeric arsinogaHane to gallium arsenide has also been described (18). GaUium arsenide has important appHcations in the field of optoelectronic and microwave devices (see Lasers Microwave technology Photodetectors). 

Arsenic and antimony are metalloids. They have been known in the pure state since ancient times because they are easily obtained from their ores (Fig. 15.3). In the elemental state, they are used primarily in the semiconductor industry and in the lead alloys used as electrodes in storage batteries. Gallium arsenide is used in lasers, including the lasers used in CD players. Metallic bismuth, with its large, weakly bonded atoms, has a low melting point and is used in alloys that serve as fire detectors in sprinkler systems the alloy melts when a fire breaks out nearby, and the sprinkler system is activated. Like ice, solid bismuth is less dense than the liquid. As a result, molten bismuth does not shrink when it solidifies in molds, and so it is used to make low-temperature castings. 

Vander Veen, M. R., Gallium Arsenide Sandwich Lasers, Advanced Mat. Processes, pp. 29-45 (May 1988)... 

Silicon is not as prominent a material in optoelectronics as it is in purely electronic applications, since its optical properties are limited. Yet it finds use as a photodetector with a response time in the nanosecond range and a spectral response band from 0.4 to 1.1 im, which matches the 0.905 im photoemission line of gallium arsenide. Silicon is transparent beyond 1.1 im and experiments have shown that a red light can be produced by shining an unfocused green laser beam on a specially prepared ultrathin crystal-silicon slice.CVD may prove useful in preparing such a material. 

D.M. Zehner, Surface Studies of Pulsed Laser Irradiated Semiconductors D.H. Lowndes, Pulsed Beam Processing of Gallium Arsenide R.B. James, Pulsed C02 Laser Annealing of Semiconductors R. T. Young and R.F. Wood, Applications of Pulsed Laser Processing... 

Gallium arsenide (Ga + As — GaAs) is electroluminscent in infrared hght and is used for telephone equipment, lasers, solar cell, and other electronic devices. 

Soft metal similar to aluminum gallium arsenide is used extensively in laser lights, electronic displays, CD players used to detect subatomic particles known as neutrinos. 

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