Semiconductor diodes

Muller R et al 1996 Time-resolved identification of single molecules in solution with a pulsed semiconductor diode laser Chem. Phys. Lett. 262 716-22... 

A semiconductor laser takes advantage of the properties of a junction between a p-type and an n-type semiconductor made from the same host material. Such an n-p combination is called a semiconductor diode. Doping concentrations are quite high and, as a result, the conduction and valence band energies of the host are shifted in the two semiconductors, as shown in Figure 9.10(a). Bands are filled up to the Fermi level with energy E. ... 

Semiconductor diodes Semiconductor industry Semiconductor lasers... 

Fig. 11. Schematic diagram of semiconductor diode laser where the junction is ca 1 ]lni. Other dimensions are <1 mm.

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

Because there are two changes ia material composition near the active region, this represents a double heterojunction. Also shown ia Figure 12 is a stripe geometry that confines the current ia the direction parallel to the length of the junction. This further reduces the power threshold and makes the diffraction-limited spreading of the beam more symmetric. The stripe is often defined by implantation of protons, which reduces the electrical conductivity ia the implanted regions. Many different stmctures for semiconductor diode lasers have been developed. 

Fig. 13. Availability of semiconductor diode lasers where represents the Al Gaj As system, UIn..Gaj As Pj, and I AlInGaP. ...

For the visible and near-ultraviolet portions of the spectmm, tunable dye lasers have commonly been used as the light source, although they are being replaced in many appHcation by tunable soHd-state lasers, eg, titanium-doped sapphire. Optical parametric oscillators are also developing as useful spectroscopic sources. In the infrared, tunable laser semiconductor diodes have been employed. The tunable diode lasers which contain lead salts have been employed for remote monitoring of poUutant species. Needs for infrared spectroscopy provide an impetus for continued development of tunable infrared lasers (see Infrared technology and RAMAN spectroscopy). 

The remaining class depicted in Figure 2 is that of soHd-state devices, ie, transistors, various types of semiconductor diode amplifiers, etc. At frequencies below 1 GHz, generation of hundreds or even at the lower frequencies, kilowatts, is feasible by soHd state. Above 1 GHz power capabiHty of soHd-state sources drops. Development of efficient (- 50%) sources at about the 50 W level at S-band (2 GHz) has been demonstrated. It is reasonable to expect soHd-state sources to replace tubes for low frequency and low (<100 W) power appHcations (52). For high power or high frequency, however, tube sources should continue to prevail. 

For quantitative analysis, the resolution of the spectral analyzer must be significantly narrower than the absorption lines, which are - 0.002 nm at 400 nm for Af = 50 amu at 2500°C (eq. 4). This is unachievable with most spectrophotometers. Instead, narrow-line sources specific for each element are employed. These are usually hoUow-cathode lamps, in which a cylindrical cathode composed of (or lined with) the element of interest is bombarded with inert gas cations produced in a discharge. Atoms sputtered from the cathode are excited by coUisions in the lamp atmosphere and then decay, emitting very narrow characteristic lines. More recendy semiconductor diode arrays have been used for AAS (168) (see Semiconductors). 

A photovoltaic cell is basically a semiconductor diode consisting of a junction similar to the junction of a transistor. An electrical potential is formed by n-type doping on one side and p-type on the other. Under the impact of light (photons), such as in sunlight, electrons move from the p side, across the junction to the n side, and, through electrical contacts, can be drawn as a usable current (Fig. 15.4). 

The pump source in the dispersive experiment is typically a nanosecond laser the probe source can be broadband IR light from a globar or tunable IR light from a CO laser or a semiconductor diode laser. Although CO and diode lasers can produce... 

The development of semiconductor diode lasers with wavelengths shorter than those used for CD-based systems means that there is a need for dyes which can exploit these wavelengths (635-650 nm) to obtain higher-density data storage, as in DVD media. Azo metal-chelate dyes can have absorption maxima in the appropriate region, and, coupled with their excellent light resistance and durability, are possible candidates for use in this respect. However, their recording and readability characteristics need to be improved. 

P. Estrela, P. Migliorato, H. Takiguchi, H. Fukushima, and S. Nebashi, Electrical detection of biomolecular interactions with metal-insulator-semiconductor diodes. Biosens. Bioelectron. 20, 1580-1586 (2005). 

There are a number of papers in the literature concerning the formation of compound semiconductor diodes by electrodeposition, the most popular structure being a CdS-CdTe based photovoltaic. CdS was generally deposited first on an ITO on glass substrate, followed by a layer of CdTe, usually by codeposition [51, 204-213],... 

Yu HZ, Liu YJ (2003) Alkyl monolayer passivated metal-semiconductor diodes 2 Comparison with native silicon oxide. ChemPhysChem 4 335-342... 

In EDXRF the secondary X-ray emitted by the excited atom is considered to be a particle (an X-ray photon) whose energy is characteristic of the atom whence it came. The major development which has facilitated this technique is the solid state semiconductor diode detector. An EDXRF system consists of a solid state device which provides an electronic output that is... 

Figures 2.13(a) and 2.13(b) illustrate the basis of a semiconductor diode laser. The laser action is produced by electronic transitions between the conduction and the valence bands at the p-n junction of a diode. When an electric current is sent in the forward direction through a p-n semiconductor diode, the electrons and holes can recombine within the p-n junction and may emit the recombination energy as electromagnetic radiation. Above a certain threshold current, the radiation field in the junction becomes sufficiently intense to make the stimulated emission rate exceed the spontaneous processes.

For the last decade, semiconductor diode-laser sensors have been developed at Stanford University for measurements of important parameters in laboratory-and industrial-scale gaseous flowfields. For example, a mass flux sensor was developed based on rapid measurements of O2 absorption near 760 nm in supersonic flowfields [1] and a multiplexed sensor was developed for the simultaneous measurement of various pollutants representing unburned hydrocarbons (CH4, CH3CI) near 1.65 pm [2]. 

We would now like to use PSpice to obtain the I-V characteristic of a semiconductor diode. Wire the circuit shown... 

If we place n- and p-type semiconducting crystals in contact (a p-n junction), we create a device that conducts electricity preferentially in one direction this is the basis of action of the semiconductor diodes used in the electronics industry, although specially refined silicon (Section 17.8.2) is usually employed rather than Ge. Transistors and electronic chips are designed using similar basic principles—typically with n-p-n or p-n-p junctions. We consider chemical aspects of electronic devices in more detail in Chapter 19. 

C. Schmeiser, On strongly reverse biased semiconductor diodes, to appear. 

Some spectrophotometric techniques work to enhance sensitivity or utility in other ways. The advent of semiconductor diode array detectors permits entire spectra to be acquired simultaneously instead of one wavelength band at a time. Also, automated spectrophotometric analyzers originally developed for clinical use have been adapted for use at sea when many samples... 

The characteristic curve of a semiconductor diode is shown in Fig. 3. An equation for this curve, called the rectifier equation, is expressed as ... 

The idea for using diodes for generation and amplification of power at microwave frequencies was suggested by A. Uhlir, Jr. Frequency multipliers have been used for power generation since 1958. These devices depend on the nonlinear reactance or resistance characteristics of semiconductor diodes. Generally, there are three types of multiplier diodes—step recovety diodes, variable resistance multiplier diodes, and variable capacitance multiplier diodes. 

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