Trapping lifetime and carrier mobility measurements in CuInSe(2 ) using surface-acoustic-wave technique

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Physics

Background:

• Copper indium diselenide (CuInSe2) is a crucial material for thin-film solar cells.
• Understanding charge carrier dynamics and defect properties is essential for optimizing semiconductor device performance.
• Trapping phenomena significantly influence carrier transport and recombination in semiconductors.

Purpose of the Study:

• To introduce and validate a novel acoustoelectric current frequency spectrum technique for characterizing trap states in p-type CuInSe2.
• To determine the trapping time constants of dominant traps in CuInSe2 under different conditions (room temperature and illumination).
• To measure minority and majority carrier mobilities and estimate carrier concentration in the material.

Main Methods:

• Utilized a novel technique measuring the frequency spectrum of the acoustoelectric current.
• Applied the method to p-type CuInSe2 samples at room temperature and under white incandescent light.
• Determined trapping time constants, carrier mobilities, and carrier concentration.

Main Results:

• Identified two dominant trap levels at room temperature with time constants of 2x10(-4) s and 6.7x10(-5) s.
• Detected two additional trap levels under illumination with time constants of 1.4x10(-3) s and 6x10(-4) s.
• Measured electron and hole mobilities as 6+/-3 cm(2)/V-s and 3.1+/-0.15 cm(2)/V-s, respectively, with a hole concentration of approximately 5x10(15) cm(-3).

Conclusions:

• The acoustoelectric current frequency spectrum technique is effective for characterizing trap states in p-type CuInSe2.
• The presence of multiple trap levels and their time constants were quantified under varying conditions.
• The study provides key parameters for understanding charge transport and potential device applications of CuInSe2.