A lower value [V.sub.oc] is obtained for the samples [B.sub.3] and [B.sub.4] due to the low value of [R.sub.sh], high surface recombination velocity
. The length of nanowires of samples [B.sub.3] and [B.sub.4] is higher (~1.5 [micro]m) than that of the other samples, so the surface recombination velocity
is increased due to increase in active surface area (number of dangling bonds).
The surface recombination velocity
is calculated using the proposed model and using SRH classical recombination adapted to the surface.
The modeling of photovoltaic devices is not simple; it depends heavily on several intrinsic optoelectronic properties of the material, such as surface recombination velocity
and volume, lifetime of minority carriers, and the doping level which is one of the extrinsic parameters which play an essential role.
In this work, the gated-diode method is used to identify the interface-trapped charge density ([N.sub.it]), the surface recombination velocity
([s.sub.o]), and the minority carrier lifetime ([[tau].sub.FIJ]) in the field-induced depletion region for the nMOSFET devices using Hf[O.sub.2] gate dielectrics annealed at 500[degrees]C.
From (2), a better surface passivation and henceforth a lower front surface recombination velocity
[S.sub.n] reduce [J.sub.o].
Vanhellemont, "Excess carrier cross-sectional profiling technique for determination of the surface recombination velocity
," Materials Science in Semiconductor Processing, vol.
Nevertheless, the IQE between 350-500 nm of the S3 cell is slightly lower than that of S2 cell, which can be explained as follows: (1) the surface state density at Si-Si[O.sub.2] interfaces is much lower than that of Si-Si[N.sub.x] interfaces , which leads to the lower surface recombination velocity
of S2 cell; (2) the surface doping concentration of S2 is reduced by thermal oxidation process which leads to the suppressing Auger recombination.
Lastly, each interface of the complete structure considers surface recombination which is parameterized using a surface recombination velocity
(SRV) according to the standard interface recombination formalism .
Generally, the EQE response of a solar cell can be attributed to the following three factors: the absorption coefficient of the active layer, surface recombination velocity
, and minority carrier lifetime .
An antireflection coating (ARC) of silicon nitride (Si[N.sub.x]:H) with a thickness of approximately 70 nm was then deposited by using a plasma-enhanced chemical vapor deposition (PECVD) in order to reduce the surface recombination velocity
. The rear surface of the silicon wafer was also passivated by depositing the same Si[N.sub.x]:H film for the measurements of the QSSPC.
According to Fisher formula the effective rear surface recombination velocity
(Seff) can be written as
where W is the sample thickness and S is surface recombination velocity
. In order to study the surface passivation of ALD Ti[O.sub.2] thin films, we used FZ n-type Si substrate which has very large bulk lifetime.