Carrier diffusion length

Lp = D r ) is the minority carrier diffusion length for electrons in the -region, (0) is the minority carrier concentration at the boundary between the depletion layer and the neutral region. The sign of this equation indicates that electron injection into the -region results in a positive current flow from p to n a.s shown in Figure 7. 

Urp Pi 1 — / If) where Wis the base width, is the distance between emitter and collector junctions and is the minority carrier diffusion length ia the... 

Obtaining information on a material s electronic band structure (related to the fundamental band gap) and analysis of luminescence centers Measurements of the dopant concentration and of the minority carrier diffusion length and lifetime... 

Many inorganic solids lend themselves to study by PL, to probe their intrinsic properties and to look at impurities and defects. Such materials include alkali-halides, semiconductors, crystalline ceramics, and glasses. In opaque materials PL is particularly surface sensitive, being restricted by the optical penetration depth and carrier diffusion length to a region of 0.05 to several pm beneath the surface. 

Gautron J, Lemasson P (1982) Photoelectrochemical determination of minority carrier diffusion length in 11-VI compounds. J Cryst Growth 59 332-337... 

An interesting question is whether such well-ordered pore arrays can also be produced in other semiconductors than Si by the same electrochemical etching process. Conversion of the macropore formation process active for n-type silicon electrodes on other semiconductors is unlikely, because their minority carrier diffusion length is usually not large enough to enable holes to diffuse from the illuminated backside to the front. The macropore formation process active in p-type silicon or the mesopore formation mechanisms, however, involve no minority carrier diffusion and it therefore seems likely that these mechanisms also apply to other semiconductor electrodes. 

The basic idea of most diffusion length measurement techniques is to generate a certain number of minority carriers inside the bulk Si, for example by illumination, and to measure the fraction of these carriers that diffuse to a collecting interface. This fraction can be determined capacitively [Bo6], as well as by measurements of the steady-state photocurrent [Dr2, Lei 1], The parameter obtained by these measurements is the minority carrier diffusion length ID of electrons in... 

For not too low doped samples (D W), however, the contribution of 1SCR is usually negligible. If the surface recombination velocity at the illuminated front is low, IBPC then only depends on sample thickness D, illumination intensity eP, and minority charge carrier diffusion length ID. 

The space charge region is denoted by length w, while Lp is the hole (minority carrier) diffusion length. Zp is the minority carrier (hole) lifetime, jp the (minority carrier) hole mobility, and Dp the minority carrier diffusion coefficient. 

A high gain transistor requires a nearly equal to 1. In the absence of collector junction breakdown, a is the product of the base transport factor and emitter efficiency. The base transport factor, aT, is the fraction of the minority current (electrons for an n-p—n transistor) that reaches the collector. ocT 1 — W2 /2L, where W is the base width, is the distance between emitter and collector junctions and Lg is the minority carrier diffusion length in the base. High gain transistors require a thin base as well as a long minority carrier lifetime for a large Lg. Because aT is >0.995 in modem transistors, there is little room for improvement. The emitter efficiency, the fraction of emitter current due to minority carriers injected into the base instead of the emitter,... 

There have been many investigations of photoinduced effects in -Si H films linked to material parameters. Changes have been observed in the carrier diffusion length, unpaired spin density, density of states in the gap, and infrared transmission. The transition from state A to B seems to be induced by any process that creates free carriers, including x-ray radiation and injection (double) from the electrodes. Because degradation in a solar cell is accentuated at the open-circuit voltage conditions, the A to B transition occurs upon recombination of excess free carriers in which the eneigy involved is less than the band gap. It has been pointed out that this transition is a relatively inefficient one and the increase in spin density takes place at a rate of 10-8 spins per absorbed photon. 

Other indirect methods for measuring lifetimes often involve device structures such as p-n junctions. The electron-beam-induced current (EBIC) technique, for example, measures the increase injunction current as an impinging electron beam moves close to the junction, i.e., within a few minority-carrier diffusion lengths. If a diffusion constant can be estimated, say by knowledge of the minority-carrier mobility, then the minority-carrier lifetime can be calculated. However, SI GaAs does not form good junctions, so such methods are really not applicable. 

Figure 16. Schematic of the influence of steps on diffusion processes in case d > > W. The lined areas indicate the extension of the depletion layer parallel or perpendicular to the layered structure, WM and W1, respectively, and I denotes the minority carrier diffusion length perpedicular to the layered structure (the horizontal radius of the ellipses is compressed somewhat).

Other intrinsic characteristic parameters of LAPS have been investigated by different research groups such as the chemical response time, the surface-state densities and zeta potential (for Si3N4), and the minority carrier diffusion length for resolution estimations. For a more detailed description of these experimental set-ups, see, e.g., Refs. [57-61],... 

M. Sartore, M. Adami, C. Nicolini, L. Bousse, S. Mostarshed and D. Hafeman, Minority carrier diffusion length effects on light-addressable potentiometric sensor (LAPS) devices, Sens. Actuators A Phys., 32(1-3) (1992) 431-436. 

Owing to its extraordinary chemical stability, diamond is a prospective electrode material for use in theoretical and applied electrochemistry. In this work studies performed during the last decade on boron-doped diamond electrochemistry are reviewed. Depending on the doping level, diamond exhibits properties either of a superwide-gap semiconductor or a semimetal. In the first case, electrochemical, photoelectrochemical and impedance-spectroscopy studies make the determination of properties of the semiconductor diamond possible. Among them are the resistivity, the acceptor concentration, the minority carrier diffusion length, the flat-band potential, electron phototransition energies, etc. In the second case, the metal-like diamond appears to be a corrosion-stable electrode that is efficient in the electrosyntheses (e.g., in the electroreduction of hard to reduce compounds) and electroanalysis. Kinetic characteristics of many outer-sphere... 

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