Effective diffusion length of minority carriers in polycrystalline silicon

1984 ◽  
Vol 84 (1) ◽  
pp. 311-317 ◽  
Author(s):  
D. P. Jwhi ◽  
R. S. Srivastava
Author(s):  
D.P. Malta ◽  
M.L. Timmons

Measurement of the minority carrier diffusion length (L) can be performed by measurement of the rate of decay of excess minority carriers with the distance (x) of an electron beam excitation source from a p-n junction or Schottky barrier junction perpendicular to the surface in an SEM. In an ideal case, the decay is exponential according to the equation, I = Ioexp(−x/L), where I is the current measured at x and Io is the maximum current measured at x=0. L can be obtained from the slope of the straight line when plotted on a semi-logarithmic scale. In reality, carriers recombine not only in the bulk but at the surface as well. The result is a non-exponential decay or a sublinear semi-logarithmic plot. The effective diffusion length (Leff) measured is shorter than the actual value. Some improvement in accuracy can be obtained by increasing the beam-energy, thereby increasing the penetration depth and reducing the percentage of carriers reaching the surface. For materials known to have a high surface recombination velocity s (cm/sec) such as GaAs and its alloys, increasing the beam energy is insufficient. Furthermore, one may find an upper limit on beam energy as the diameter of the signal generation volume approaches the device dimensions.


1992 ◽  
Vol 280 ◽  
Author(s):  
F. L. Metcalfe ◽  
J. A. Venables

ABSTRACTCrystal growth and surface diffusion have been studied in the Ag/Ge(lll) system using UHV-SEM based techniques, biassed secondary electron imaging (b-SEI), micro-AES and RHEED. Ag was deposited through and past a mask of holes held close to the substrate at 300<Td< 775K. Under certain conditions, the Ag patches were observed to split into two regions corresponding to the √3×√3R30° (hereafter √3) and a lower coverage 4×4 structure, each of which were easily observable using b-SEI. These patch widths were measured as a function of Td, and of annealing times at temperatures Ta, and effective diffusion coefficents extracted. The diffusion length of adatoms over the 4×4 structure is larger than that over the √3 structure. These observations are modelled using kinetic rate equations, and the results are compared with previous studies of Ag/Si(111). We find that energies characterising processes on top of the √3 layers of both systems are very similar, but that processes involved in the formation of the layers are quite different. The coverage of the √3 Ag/Ge(111) layer is close to 1 ML for all Td studied, unlike √3 Ag/Si(111). where it depends on deposition and annealing conditions.


1971 ◽  
Vol 4 (1) ◽  
pp. 249-255 ◽  
Author(s):  
S. Rakshit ◽  
S. N. Biswas ◽  
A. N. Chakravarti

1997 ◽  
Vol 71 (15) ◽  
pp. 2121-2123 ◽  
Author(s):  
A. A. Istratov ◽  
C. Flink ◽  
H. Hieslmair ◽  
T. Heiser ◽  
E. R. Weber

2019 ◽  
Vol 3 (10) ◽  
pp. 2597-2603 ◽  
Author(s):  
Seok Ho Cho ◽  
Sung-Min Lee ◽  
Kyung Cheol Choi

A simple route to enhance the efficiency of polymer solar cells is presented by exploiting plasmonically assisted photon recycling. Embedded gold nanorods promote the photon radiation from excitons, and hence improve the effective diffusion length of excitons.


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