Investigation of V-groove fabricated GaInNAs nipi solar cell structure

Abstract

An anisotropic etching of 1 eV Ga0.92In0.08N0.03As0.97 grown on (100) p-type GaAs substrate was investigated. Effects of the V-groove etching profile and metallization on the photovoltaic performance of the GaInNAs nipi solar cell with five periods are presented. Experimental results were supported by simulation studies considering the metal–semiconductor junction characteristics in the electrodes of nipi photovoltaic device. Standard wet etching processes at room temperature is applied using sulfuric acid based H2SO4: H2O2: H2O [1:8:8] solution to form the V-groove shape on the nipi sample. The etching characteristics in the [100] and $$\left\langle {011} \right\rangle$$ crystal directions are determined by using an interdigitated square spiral photolithographic mask. The scanning electron microscope (SEM) is used to analyze the V-groove etch profile. Two type of V-grooves achieved, one of them is in the $$\left[ {1\bar{1}1} \right]$$ direction and suitable to form metal electrodes for nipi layers and the second one is in $$\left[ {\bar{1}11} \right]$$ direction can be called a dovetail groove and not suitable for metal coating. Experimentally, the improvements observed in the short circuit current, open circuit voltage, and efficiency of the device despite some metallization failures. The effect of the metallization quality on the response to the spectrum can be clearly seen from the photovoltage spectrum. Essentially, these experimental results show that GaInNAs nipi devices have the potential to become high efficiency solar cells. Moreover, it can be possible to achieve high performance by integrating nipi devices into multijunction solar cells.