Improved Leakage Current, Output Power, and
Electrostatic Discharge Characteristics of GaN LEDs by
Chemical Etching
Tae-Young Park, Chang-Hee Cho, Il-Kyu Park, and Seong-Ju Park
Outline

Introduction

Experiment

Results and Discussions

Conclusions

References
Introduction
Investigated the effect of chemical etching of the pGaN surface on the leakage current, light output power,
and ESD characteristics of GaN LEDs.
Experiment
Ni/Au(30/80nm)
Ni/Au(5/5nm) current spreading layer
P
MQW
Mg(2×1020cm-3)-doped p-GaN(0.13 μ m)
5- period-InGaN(3nm)/GaN(7nm)
N
Si(9×10-18cm-3)-doped n-GaN(2 μ m)
sapphire substratrs
LED size 300 ×300 μ m
Ti/Al(30/80nm)
Results and Discussions
CFB = 1/1/Cox + LD/εs
Cox ：氧化物電容3.5 10−11 F
LD ：德拜（Debye）長度
1.02 10−8 m
εs ： GaN介電常數8.9
德拜長度：
一方面是靜電作用的屏蔽半徑
一方面是區域性電荷分離的空
間尺度。
量測電容Sample：
Al(100nm)/SiO2(15nm)/p-GaN(1μm)/u-GaN(2μm)
Figure 1. Color online C-V curves for nonetched and etched p-GaN MOS capacitor devices at
100 kHz.
DDAP ：施子與淺層受子對，波峰是決定於摻雜的鎂濃度大小。
鎂摻雜濃度較高時，只能觀察到2.8eV 的波峰。
Mg
GaN
Figure 2. Color online Room-temperature PL spectra for the etched and nonetched p-GaN layer.
7×10-8
3×10-6
1×10-5
1×10-9
Figure 3. Color online Current–voltage curves at a forward bias b reverse bias voltage in the
nonetched and etched GaN LEDs.
Figure 5. Color online ESD characteristics of the nonetched and etched GaN LEDs: a forward
voltage measured at 20 mA after application of positive-voltage ESD stress and b forward voltage
measured 20 mA after application of negative-voltage ESD stress.
58% at 20mA
Figure 4. Color online Light output power of etched and nonetched GaN LEDs as a function of
injection current.
Conclusions
Defects were densely concentrated near the surface region ~18 nm of the p-GaN
layer and were effectively removed by using a molten KOH and NaOH solution. The
defect-assisted leakage currents at the forward and reverse bias voltage were
remarkably decreased due to a reduction of DDAP defect, and the light output power of
etched GaN LEDs was significantly improved by 58% at an injection current of 20 mA
due to enhanced injection efficiency. The negative-voltage ESD characteristics of GaN
LEDs were also improved from −0.3 to − 0.9 kV.
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