Semiconductors radiation damage

The method is essentially non-destructive, although in some circumstances a target may suffer radiation damage. For example the lattice site position of some dopants in semiconductors can be influenced by RBS analysis. With a typical analysis time of less than 30 min, it is a relatively quick method. Its most important characteristic is... 

Corbett, J.W. (1966). Electron Radiation Damage in Semiconductors and Metals, Academic press, N.Y. 

Watkins, G. D. In Radiation Damage in Semiconductors Institute of Physics Bristol, 1973 p 228. 

Electron paramagnetic resonance (EPR) is a spectroscopic technique detecting chemical species that have unpaired electrons. A great number of materials contain such paramagnetic entities, which may occur either as electrons in unfilled conduction bands, electrons trapped in radiation damaged sites, or as free radicals, various transition ions, biradicals, triplet states, impurities in semiconductors, as well as other types. Solids, liquids and gases are all accessible to EPR. 

In contrast to the methods described in the preceding paragraphs, radiophotovoltaic conversion is a direet method. In a semiconductor the incident radiation generates free charge carriers, that are separated in the n,p-barrier layer of the semiconductor. Suitable radiation sources are radionuclides emitting p particles with energies below the limits of radiation damage in the semiconductors. These limits are about 145 keV for Si and about 350 keV for Ge. Therefore only Pm, Ni and T are suitable as radiation sources. By use of the combination Pm/Si, efficiencies of about 4% are obtained. 

While a lot of work has been done with heavy-ion induced radiation damage in metals and semiconductors, very little has been done on compounds, especially on covalent ones. In the following section we shall try to cover the most important work on the radiation chemistry of compounds. In the section on metals only a few selected examples will be mentioned. In the last part of this chapter we shall deal with changes in the composition of surfaces due to sputtering of compounds. 

We have already mentioned that radiation damage in metals and semiconductors is beyond the scope of this review. It is, nevertheless, interesting to compare the results for compounds described in the preceding section with the measurements for metals and elemental semiconductors. 

In Table 4 the irradiation conditions for various metals, semiconductors and compounds together with the dose at which the radiation damage tends to saturate are listed. This does not necessarily mean complete amorphization. The values for Si give an impression of the increasing magnitude of the effects if one goes from light to heavy ions. The data are from the studies mentioned above and from ... 

G.D. Watkins, in Radiation Damages in Semiconductors, Paris-Royaumont 1964, ed. by P.Baruch (Dunod, Paris, 1964), pp. 97-113... 

Less data are available on decay after-effects from "Te. A matrix of PbTe irradiated with neutrons was found to have a chemical isomer shift of over +0-1 mm s relative to a PbTe absorber [56]. Furthermore this shift difference decreased exponentially with a time constant of about ten days, the implication being that the difference is due to radiation damage causing a defect structure which anneals at room temperature. It was proposed that a radiation-induced distortion of the band structure in the PbTe semiconductor alters the s-electron density at the nucleus. 

The fabrication and operation of a semiconductor detector are based on the premise that one starts with a perfect crystal containing a known amount of impurities. Even if this is true at the beginning, a semiconductor detector will suffer damage after being exposed to radiation. The principal type of radiation damage is caused by the collision of an incident particle with an atom. As a result of the collision, the atom may be displaced into an interstitial position, thus creating an interstitial-vacancy pair known as the Frenkel defect. A recoiling... 

The basic mechanisms of radiation damage in semiconductor devices are as follows ... 

Recently, both steady-state and pulsed fast neutron generators have been applied to the investigation of radiation damage of metals, alloys, semiconductors, and high Tc ceramics and to nuclear heating of superconductors by prompt reaction products and long-lived radioisotopes. Of the wide range of applications a few typical examples are discussed in this review (Csikai 1995). 

---