电流阻挡层对大功率LED光电热特性的影响

doi:10.3964/j.issn.1000-0593(2020)02-0368-05

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Abstract As the core of LED light source, the quality of LED chip directly determines the performance, life and so on of the device. Therefore, the improvement of optical extraction efficiency is the key step to promote the development of LED chip technology when the internal quantum efficiency has reached a fairly high level. Due to the insulating property of sapphire, the N and P electrodes of normal LED are made on the same side of the light output surface of the chip. The P metal electrode on the light output surface absorbs most of the light emitted from the luminous region directly below it, and causes light loss. To improve this phenomenon and alleviate the current crowding around the P electrode, in this paper, we fabricated LED devices with SiO₂ current blocking layer（CBL）that was deposited between ITO transparent conductive layer and P-GaN,and another kind of LED without CBL. We tested voltage，light output power，main wavelength of the two kinds of chips without package under 350mA working current. The results showed that the forward voltage of the two kinds of chips are concentrated in 3~3.1V, while the light output power of the LED with CBL is obviously improved. CBL blocks the current from diffusing below the P electrode and reduces the current density flowing to the active region, thus reducing the absorption and shielding of light by the P electrode, and directing the current to the region far away from the P electrode through CBL, reducing current congestion around the electrode. Then the two kinds of chips were packaged in the same package structure and process conditions. The thermal characteristics and photoelectric properties of two samples were investigated under different current range from 10 to 600 mA, and the spectra and optical power of two kinds of devices were obtained. Results showed that main wavelength of the two samples blue shift with the increasing current, and the main wavelength blue-shifting of LED with CBL is 10nm less than the LED without CBL. It can be seen that the spectra of LED inserted CBL is less affected by the increasing current. Therefore, its color rendering properties is more stable. Under the low current, CBL structure has little effect on the optical power of the device. With the increase of current, the improvement effect of CBL on the optical power is improved gradually. Under the heavy current, the junction temperature of the LED without CBL is higher and the forward voltage is lower, and the voltage difference between the two kinds of devices increases with the increasing current. Under 25℃ ambient temperature, 350 mA working current, the voltage of LED with CBL increases 0.04 V, but it improves optical power, the highest increase is 9.96%, and the thermal resistance is obviously smaller than the device without CBL structure, which indicates that the heat production of LED with CBL is less than the device without CBL structure. Therefore, the optical extraction efficiency of the device is improved by CBL structure. And the spectrum drifting is smaller and the color rendering properties is more stable.

Key words：Highpower LED；Current blocking layer（CBL）；Light output power；Spectra；Thermal resistance

Received: 2018-12-25 Accepted: 2019-04-08

ZTFLH:

O462.3

Corresponding Authors: GUO Wei-ling E-mail: guoweiling@bjut.edu.cn

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2020)02-0368-05 OR https://www.gpxygpfx.com/EN/Y2020/V40/I02/368