Lateral Current Spreading Effect on the Efficiency Droop in GaN Based Light-Emitting Diodes

Abstract

The lateral current spreading (CS) effect on the efficiency droop in GaN-based LEDs has been studied in terms of the CS distance using a designed pattern with the 2-D current spreading profile. The correlations of CS effect with the electrical, luminescent and electric-thermal properties of the LEDs have been discussed. LEDs with the longer than the theoretically calculated effective CS length suffer from more serious efficiency droop and the degradation of luminescent properties. However, the influence of CS effect on the ideality factors of LEDs is not obvious. Higher chip temperature caused by poor CS was observed and may further enlarge the efficiency droop.

Enhanced emission from mid-infrared AlInSb light-emitting diodes with p-type contact grid geometry

“…9,22 The characterisation of local current distribution in mid-IR emitting LEDs is more demanding. The experimental results reported so far, in fact, require high-resolution timeresolved IR microscopy, performed with expensive focal plane arrays operating at cryogenic temperatures.…”

“…This geometry is similar to widely reported GaN-based LEDs, where current crowding effects due to the relative resistivities of the n-and p-type doped regions have been extensively studied. [6][7][8][9] At visible wavelengths, these issues can be mitigated by the use of transparent conductive layers (TCLs) such as indium tin oxide. However, these cannot be employed in surface-emitting mid-IR LEDs due to their high reflectivity in this spectral range.…”

Theoretical considerations on efficiency degradation due to thermal effect in a planar GaN-based LED with a GaN substrate

“…[12][13][14][15][16][17][18] In order to investigate these thermal effects on the LED properties, coupled electro-thermal simulations have been implemented. [14][15][16][17][18][19][20][21][22][23] Among those studies, a hybrid model of the electrical, optical and thermal processes as described in the paper of Bogdanov et al, 16) has successfully simulated current flowing, heat transfer, light emission, and light extraction; it has provided a qualitative understanding for the efficiency degradation and series resistance variation due to self-heating. 14) Although that hybrid approach is simple and helps to reduce computational time, its accuracy for modeling current spreading is insufficient.…”

Performance Enhancements of Flip-Chip Light-Emitting Diodes With High-Density n-Type Point-Contacts

“…Better light extraction can be improved via the use of surface texture or a patterned substrate [4]. Current crowding and efficiency droop can be minimized by growing a more conductive GaN layer, modifying the mesa geometry or electrode patterns [5]- [7].…”