INSTITUTE OF PHYSICS PUBLISHING SEMICONDUCTOR SCIENCE AND TECHNOLOGY Semicond. Sci. Technol. 19 (2004) 213–218 PII: S0268-1242(04)66550-3 Comparative secondary ion mass spectroscopy analysis of solar cell structures grown by pulsed laser ablation and ion sputtering J A Godines 1 , A Villegas 1 , Yu Kudriavtsev 1 , R Asomoza 1 , A Morales-Acevedo 1 , A Escamilla 2 , G Arriaga 2 , H Hern´ andez-Contreras 2 , G Contreras-Puente 2 , J Vidal 2 , M Chavarr´ ıa 2 and R Fragoso-Soriano 3 1 CINVESTAV-IPN, Depto Ingenier´ ıa El´ ectrica-SEES, Av IPN # 2508, CP 07360 M´ exico, DF, Mexico 2 Escuela Superior de F´ ısica y Matem´ aticas del IPN, Zacatenco, M´ exico, DF, Mexico 3 CINVESTAV-IPN, Depto F´ ısica, Av IPN # 2508, CP 07360 M´ exico, DF, Mexico E-mail: amorales@gasparin.solar.cinvestav.mx Received 22 July 2003, in final form 25 September 2003 Published 3 November 2003 Online at stacks.iop.org/SST/19/213 (DOI: 10.1088/0268-1242/19/2/015) Abstract We performed a complex secondary ion mass spectroscopy (SIMS) 3D analysis of solar cell structures based on II–VI semiconductors. The chemical composition analysis, as well as the depth distribution of the main elements and contamination were done for AuCu/CdTe/CdS/conducting glass structures. A structure where the II–VI compounds were grown by pulsed laser ablation (PLA) was compared with another structure grown by ion sputtering deposition (ISD). In both cases contamination due to O, C and H was found at high concentrations, particularly at the boundaries between crystallites. In addition to the SIMS depth profiling, the surface roughness (SR) was analysed by atomic force microscopy (AFM). Poor SIMS depth resolution was correlated to high surface roughness. The root-mean-square of the surface roughness (R rms ) was found to be higher for ISD than for PLA structures. In addition, the lateral distribution of the main components and contamination were observed in the microscope mode with a resolution of about 1 μm. A larger lateral contamination was correlated to a larger R rms of the analysed surface. Experimental ‘diffusion’ tails of Cu and Au from the ohmic contacts on the CdTe layer are also explained by a high R rms for this layer. 1. Introduction II–VI thin film semiconductors have shown great perspectives as materials for photovoltaic applications. Structures based on thin CdS and CdTe films have demonstrated high efficiencies reaching more than 16% for the best solar cells [1]. This value is less than the 24.7% record efficiency obtained for Si-based solar cells structures [2], but II–VI semiconductor solar cells are still far from the theoretical efficiency limit. In order to achieve higher efficiencies for CdS/CdTe cells some problems should be solved: • understanding the role of point defects and impurities at the CdTe/CdS hetero-junction and the ohmic contact to CdTe. • understanding the inter-diffusion between CdTe and CdS layers. • providing and controlling p-type and n-type doping for good junction formation. • smoothing the surface roughness during the growth processes (important problem for most methods of CdTe/CdS deposition). • improving the back ohmic contact technology: adhesion, 0268-1242/04/020213+06$30.00 © 2004 IOP Publishing Ltd Printed in the UK 213