Generation recombination Limit

The safety profile of recombinant AAV (rAAV) vectors is attributed to the lack of association with human disease as well as the ability to generate recombinant vectors that contain no viral genes. Similar to adenoviral vectors, AAV can infect both dividing and non-dividing cells, and has a broad tissue tropism. In contrast to adenoviral vectors, rAAV vectors have a limited packaging capacity of about 4.9 kb, limiting their use to diseases in which the deficient gene is relatively small. 

If the surface of a single crystal n-type semiconductor is damaged by abrasion or by high energy particle bombardment, the generation (recombination) velocity for holes in the surface layer is increased to the extent that holes are readily available to carry out anodic reactions at a rapid rate. This condition lasts until most of the damaged surface material is removed. Then the anode current is limited as previously described due to hole depletion. 

The Onsager charge recombination model [113-114] is commonly used for analyzing the field dependence of charge-generation efficiency. Limitations and inadequacies do exist for this model. In this section, I discuss the... 

The failures observed during measurement were the increase of Iceo over the allowed limit or reduction of the hiu beneath the imposed limit. The failure mechanism concerning increase o f generation-recombination on depth level was considered as unique. 

Up to this point the discussion has been limited to full dissociation results = k2 = 0). Some work has been published which deals with generation-recombination (GR) effects when only one charged species is mobile, but unpublished work in progress yields particularly interesting results in the r r two-mobile case (tt neither zero nor infinite). Consider tSe M 5> 1 situation with and k non-zero. Two new parameters... 

Table 3.1 shows some possible methods of application of external and/or built-in fields for generation-recombination suppression in narrow-bandgap materials. As said before, we limit ourselves to photoconductive and photovoltaic structures. Even so, it is visible that there is a number of nonequilibrium structures and modes of operation never previously investigated. 

Klipstein et al. (2010) describes these devices succinctly A new XBn device architecture, based on heterostructures, has been proposed as an alternative to a homojunction photodiode. The main difference is that no depletion layer exists in any narrow bandgap region of the device. Instead, the depletion layer is confined to a wide bandgap barrier material. The Generation-Recombination (G-R) contribution to the dark current is then almost totally suppressed and the dark current becomes diffusion limited. This lowering of the dark current allows the device operating temperature to be raised relative to that of a standard photodiode made from the same photon absorbing material, with essentially no loss of performance. 

The equihbtium lever relation, np = can be regarded from a chemical kinetics perspective as the result of a balance between the generation and recombination of electrons and holes (21). In extrinsic semiconductors recombination is assisted by chemical defects, such as transition metals, which introduce new energy levels in the energy gap. The recombination rate in extrinsic semiconductors is limited by the lifetime of minority carriers which, according to the equihbtium lever relation, have much lower concentrations than majority carriers. Thus, for a -type semiconductor where electrons are the minority carrier, the recombination rate is /S n/z. An = n — is the increase of the electron concentration over its value in thermal equihbtium, and... 

The diffusion of H and D atoms in the molecular crystals of hydrogen isotopes was explored with the EPR method. The atoms were generated by y-irradiation of crystals or by photolysis of a dopant. In the H2 crystals the initial concentration of the hydrogen atoms 4x 10 mol/cm is halved during 10 s at 4.2 K as well as at 1.9 K [Miyazaki et al. 1984 Itskovskii et al. 1986]. The bimolecular recombination (with rate constant /ch = 82cm mol s ) is limited by diffusion, where, because of the low concentration of H atoms, each encounter of the recombinating partners is preceded by 10 -10 hops between adjacent sites. 

Experimental evidence with very different semiconductors has shown that at semiconductor interfaces where limited surface recombination and a modest interfacial charge-transfer rate for charge carriers generate a peak... 

---