Frequency-Resolved Forward Capacitance in GaN-based LEDs

TL;DR

This paper introduces a comprehensive impedance model for GaN-based LEDs that clarifies frequency-dependent capacitive behaviors, including negative capacitance, by linking physical mechanisms with device engineering for improved optoelectronic design.

Contribution

The study develops a unified impedance framework that accurately interprets dynamic capacitance responses in LEDs, resolving longstanding controversies and enabling precise control of charge dynamics.

Findings

Negative capacitance arises from trap-mediated carrier emission.

Quantum well thickness modulation reduces mid-frequency capacitance by 30%.

Trap-mediated inductance dominates parasitic effects by three orders of magnitude.

Abstract

This study establishes a unified framework for interpreting dynamic capacitive responses in InGaN-based light-emitting diodes (LEDs) through forward-bias capacitance-voltage-frequency spectroscopy. A hybrid impedance model integrating series RL components and parallel C-G networks was developed to resolve distinct frequency-dependent capacitive regimes. The low-frequency regime (<1 kHz) is governed by interfacial capacitance with characteristic reciprocal frequency dependence, while the mid-frequency range(10 kHz-6.4 MHz) demonstrates carrier diffusion and recombination dynamics. At MHz frequencies, negative capacitance manifests due to delayed carrier emission mediated by deep-level traps. The model achieved sub-1% fitting errors (R^2 > 0.99)across a broad bandwidth(10 kHz-6.4 MHz) , conclusively attributing negative capacitance to intrinsic trap processes rather than extrinsic artifacts. Critical advances include quantum well cap thickness modulation reducing mid-frequency capacitance by 30% and the dominance of trap-mediated inductance over parasitic contributions by three orders of magnitude. This framework resolves persistent controversies in LED impedance interpretation. By bridging semiconductor physics with device engineering, this methodology provides essential tools for designing next-generation optoelectronic systems requiring ultralow-latency operation and precise charge-state control.