Elucidating negative capacitance in light-emitting diodes using an advanced semiconductor device theory

Abstract

The capacitance characteristics of light emitting diodes (LEDs) are accurately measured using a method based on an alternating-current small signal, together with direct current I-V plot. All measured LEDs display negative capacitance (NC) at large forward bias. By analyzing the dependence of capacitance on both forward bias and frequency, an accurate expression for describing NC was obtained. This expression is in conflict with Shockley's p-n junction theory, which only describes increasing diffusion capacitance and does not allow NC. Using an advanced p-n junction theory developed by Hess and Laux, the dependence of NC on both voltage and frequency are described quantitatively.

Role of light emission and sub‐bandgap defects in the dielectric response of electroluminescent diodes

“…It was observed that the capacitance of the r-ELDs becomes negative for sufficiently high applied biases and low modulation frequencies. This negative capacitance (NC) behaviour has been reported previously for different type of devices like solar cells [2,3], p-i-n diodes [4], Schottky diodes [5,6] metal-insulator-semiconductor structures [7] including electroluminescent diodes [1,[8][9][10][11]. However, the explanations given by various groups for the occurrences of NC do not agree to a common argument.…”

Precise relationship between voltage and frequency at the appearance of negative capacitance in InGaN diodes

“…9 In the inset of Figure 2(a), we found that after a small increase, the apparent capacitance began to decrease and then became negative. In addition, corresponding to frequencies of l kHz, 10 kHz, and 100 kHz, the voltages where NC appears were different, as indicated by A, B, and C, respectively, in Figure 2(a).…”

“…These results are similar to experimental results reported previously. 8,9 Therefore, we can use the same expression of NC:…”

“…Abnormal negative capacitance (NC) has been observed repeatedly in the AC impedance measurements of p-n and Schottky junction diodes under large bias voltage. [3][4][5][6][7][8][9][10] Unfortunately, because NC is not allowed by Shockley's p-n junction theory, which only describes increasing diffusion capacitance, 11 it is very difficult to explain NC quantitatively. In 1999, Laux and Hess proposed a complete circuit for a p-n junction that predicted the existence of NC in long and short base p-n junction diodes at large bias voltage.…”

Dynamics of electronic transitions and frequency dependence of negative capacitance in semiconductor diodes under high forward bias

“…We observed that as the forward bias increases, the reactive component of the impedance demonstrates negative capacitance (NC). Higher magnitude of this NC for lower applied modulation frequencies has also been observed by many groups in electroluminescent devices [5][6][7] and also in other semiconductor devices. 8,9 Here, we report qualitatively opposite dynamic behavior of NC in two sets of diodes with different functionalities: (a) III-V based electroluminescent diodes (ELDs): (i) InGaAs based quantum dot laser (QDL) diodes grown by Molecular Beam Epitaxy (MBE) on (100) GaAs substrates.…”