Abstract
The In-doped CdTe/Si (p) heterostruture was fabricated and its electrical and photoelectrical properties were studied and interpreted. During the fabrication processes of CdTe/Si heterojunction, some practical troubles were encountered. However, the important one was the formation of the SiO2 thin oxide layer on the soft surface of the Si during the formation of the back contact. The silicon wafer was subjected to different chemical treatments in order to remove the thin oxide layer from the silicon wafer surfaces. It was found that the heterojunction with Si (p+) substrate gave relatively high open circuit voltage comparing with that of Si (p) substrate. Also an electroforming phenomenon had been observed in this structure for the first time which may be considered as a memory effect. It was observed that there are two states of conduction, non-conducting state and conducting state. The normal case is the non-conducting state. As the forward applied voltage increased beyond threshold value, it switches into the conducting state and remains in this state even after the voltage drops to zero.
Highlights
In recent years much attention had been paid to the heterojunction devices research [1]
An electroforming phenomenon had been observed in this structure for the first time which may be considered as a memory effect
Mohamed et al [3] studied the electrical properties of post-deposition annealed and asdeposited In-doped CdTe thin films, it was observed that the CdTe film was of modified Poole-Frenkel conduction mechanism and the resistivity of the film could be lowered by more than one order of magnitude due to indium doping
Summary
In recent years much attention had been paid to the heterojunction devices research [1]. The In-doped CdTe (p) thin film is of high bulk resistivity which largely affects its photovoltaic properties the short circuit current. MOHAMMAD would probably reduce the bulk resistance and possibly improves contact performance It was proved previously [4] that the polarity of the applied voltage had almost no effect on the I-V characteristics of Al-In doped-CdTe-Al structure annealed at 100 ̊C, which means that the contacts are ohmic. It can be observed that the bulk conductivity of the doped (diffused) films is about one order higher than that of the undoped CdTe films This is due to the incorporation of Indium atoms that acts as donor sites, which in turn increases the carrier concentration. N-type Si nc on p-type bases is a possible perspective [13]
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