Electron diffusion lengths in p-type InP involved in indium tin oxide/p-InP solar cells

Abstract

Electrical and photovoltaic properties of indiumtinoxide/pInSe/Au solar cellsElectron diffusion length measurements have been performed in p-type InP by different methods: Sut?a~e photovoltage, spectrum analysis of the photocurrent in an indium tin oxide/p-lnP diode, vanatlOn of the photovoltage in this diode versus reverse voltage, and electron beam induced current measurements. The results are compared and discussed in detail. A double p-type region model with different electron diffusion lengths has been proposed to explain the experimental results.

Surface photovoltage phenomena: theory, experiment, and applications

“…The predictions of Phillips have been con®rmed experimentally by Gouskov et al [451]. These authors have extracted widely differing L values from electron beam induced current (EBIC) measurements, quantum ef®ciency curves, and SPV measurements (the latter in both contactless and short-circuit current modes) at ITO/InP heterojunctions.…”

“…This is because such measurements potentially enable the extraction of L in the absorber material inside a complete cell structure. Diffusion length values were successfully extracted from open circuit voltage measurements on solar cell junctions [433,443,444,446,449,451,455]. As long as the top region in a homojunction, or the window layer in a heterojunction, are considerably more heavily doped than the absorber (which is usually the case), the depletion region is contained almost entirely within the absorber layer, just like in the case of a free surface or a Schottky contact.…”

“…This process yields a near-surface region, known as the denuded zone, which is relatively free of metallic impurities even if the wafer quality is not very high. Chappell et al [543] suggested that such wafers may be modelled as a bulk region with low L and an epitaxial layer with high L (i.e., opposite to the ITO/InP case studied by Gouskov et al [451]). Using numerical simulations, they concluded that if the denuded zone width is between the L values of the denuded zone and the substrate, L app is proportional to the denuded zone width and may serve as an indicator of it.…”

“…These include GaAs [5,118,431,432,440,449], AlGaAs [454], InGaAs [437], InP [425,433,451,455,519,520], CdS [521], CdSe [455,521±523], ZnSe [524], CdMnTe [525], and even WSe 2 [526], Cu(In,Ga)Se 2 [463], and CdP 2 [485]. …”

Heat treatment effect on p type Zn doped InP substrates

“…Therefore the G-R lifetime TG_R can be deduced from these I-V measurements [10] 2) The variations of Ln and T versus Xj are similar, indicating that the mobility of minority carrier is homogeneous into the heat treated substrate. [12].…”