Maria Faur

Electrolyte for electrochemical C-V profiling of InP- and GaAs-based structures

Abstract A new electrolyte (UNIEL) based on HF, NH3F2, C9H14CIN, CH3COOH and o-H3PO4 has been developed for accurate EC-V net majority carrier concentration profiling of InP- and GaAs-based III–V semiconductors. The new electrolyte was tested with good results on heterostructures containing p- and n-type InP, GaAs, InGaAs and InGaAsP layers.

Closed-ampoule diffusion of sulfur into Cd-doped InP substrates - Dependence of S profiles on diffusion temperature and time

In order to optimize the fabrication of n+–p InP solar cells made by closed‐ampoule diffusion of sulfur into p‐InP:Cd substrates, we have investigated the influence of diffusion conditions on sulfur diffusion profiles. We show that S diffusion in InP is dominated by the P vacancy mechanism and is not characterized by a complementary error function as expected for an infinite source diffusion. The S diffusion mechanism in p‐InP is qualitatively explained by examining the depth profiles of S, P, and In in the emitter layer and by taking into account the presence and composition of different compounds found to form in the In–P–S–O–Cd system as a result of diffusion.

Indium Phosphide Solar Cells Made By Closed-Ampoule Diffusion Of Sulphur Into Cadmium-Doped InP Substrates: Dependence Of Cell Characteristics On Diffusion Temperature And Time

We have studied the dependence of solar cell performance characteristics on diffusion temperature and time, for cells made by the closed-ampoule thermal diffusion of S into Cd-doped InP substrates of starting doping 1.7x 1016 cm-3. Diffusions were performed at 600, 625, 650, 700, and 725°C for 3 hours, 675°C for 1, 2, 3 and 4 hours, and, on specially treated substrates with phosphorus-rich surfaces, at 650 and 660°C for 3 hours. We have measured Isc, Voc, FF, η, spectral response, J0 and A factor, series and shunt resistances, and emitter sheet resistance and specific contact resistance of front metallization. Our results indicate that for best solar cell efficiency, the diffusion temperature should be between 650 and 675°C and the diffusion time should be from 1 to 3 hours, for our Cd-doped material.

XPS, Auger And SEM Analysis Of The InP Surface After Closed-Ampoule Diffusion With Sulphur At Several Diffusion Temperatures

In an attempt to identify the factors which limit the performance of InP solar cells made by the closed-ampoule diffusion of sulphur into p-type InP substrates, and in order to optimize the fabrication process, we have done a detailed analysis of the InP surface and of the diffused emitter region using XPS, Auger, SEM and EDAX for diffusion temperatures of 600, 625, 650, 675, 700 and 725°C for a fixed diffusion time of 3 hours, and diffusion times of 1, 2, 3, and 4 hours for a fixed temperature of 675°C. In this paper, we present the results of this analysis, showing how the morphology and chemical composition of the InP surface layer changes with the diffusion temperature and identifying the possible mechanisms which limit the photocurrent and the open circuit voltage of solar cells fabricated using the closed-ampoule diffusion process.