Photoemission Study of GaN Passivation Layers and Band Alignment at GaInP(100) Heterointerfaces.

Area of Science:

• Materials Science
• Semiconductor Physics
• Electrochemistry

Background:

• III-V semiconductor devices, particularly those with GaInP top photoabsorbers, exhibit high solar conversion efficiencies.
• III-V semiconductors in photoelectrochemical (PEC) cells require robust passivation layers for stability and performance.
• Gallium nitride (GaN) is a promising candidate for passivation layers due to its material properties.

Purpose of the Study:

• To investigate the band alignment between GaN passivation layers and n-type GaInP(100) photoabsorbers.
• To evaluate the suitability of GaN as a passivation layer in PEC cells by analyzing interfacial properties.
• To understand the role of GaN in charge carrier transport and surface passivation.

Main Methods:

• Epitaxial growth of n-type GaInP(100) on oxidized GaAs(100) substrates.
• Deposition of 1-20 nm GaN films using atomic layer deposition.
• X-ray and ultraviolet photoelectron spectroscopy (XPS/UPS) to study band alignment at the GaN/GaInP interface.

Main Results:

• Characterized surface band bending (BB) of n-GaInP(100) and its reduction upon oxidation.
• Determined valence band offset (VBO) between GaInP(100) and a thin oxide layer (2.01 eV).
• Quantified VBO (1.90 eV) and conduction band offset (CBO) (0.44 eV) between GaInP(100) and GaN, indicating favorable band alignment.

Conclusions:

• GaN is confirmed as a suitable passivation layer for III-V photoabsorbers in PEC applications.
• The determined band alignment facilitates selective transport of photogenerated electrons.
• GaN passivation enhances the stability and efficiency of PEC devices.