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Fabrication and characterization of GaN-based light-emitting diodes without pre-activation of p-type GaN.

Hu XL, Wang H, Zhang XC - Nanoscale Res Lett (2015)

Bottom Line: During the fabrication process, a 100-nm-thick indium tin oxide film was served as the p-type contact layer and annealed at 500°C in N2 ambient for 20 min to increase its transparency as well as to activate the p-type GaN.We discussed the mechanism of activation of p-type GaN at 500°C in N2 ambient.Furthermore, x-ray photoemission spectroscopy examinations were carried out to study the improved electrical performances of the LEDs without pre-activation of p-type GaN.

View Article: PubMed Central - PubMed

Affiliation: Engineering Research Center for Optoelectronics of Guangdong Province, School of Physics and Optoelectronics, South China University of Technology, Guangzhou, Guangdong 510640 China.

ABSTRACT
We fabricated GaN-based light-emitting diodes (LEDs) without pre-activation of p-type GaN. During the fabrication process, a 100-nm-thick indium tin oxide film was served as the p-type contact layer and annealed at 500°C in N2 ambient for 20 min to increase its transparency as well as to activate the p-type GaN. The electrical measurements showed that the LEDs were featured by a lower forward voltage and higher wall-plug efficiency in comparison with LEDs using pre-activation of p-type GaN. We discussed the mechanism of activation of p-type GaN at 500°C in N2 ambient. Furthermore, x-ray photoemission spectroscopy examinations were carried out to study the improved electrical performances of the LEDs without pre-activation of p-type GaN.

No MeSH data available.


Current-voltage and dynamic resistance characteristics of the LED samples A, B, and C, respectively.
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Fig2: Current-voltage and dynamic resistance characteristics of the LED samples A, B, and C, respectively.

Mentions: Figure 2 shows the current-voltage and dynamic resistance characteristics of the LED samples A, B, and C. The forward voltage is the average value of 100 LED chips which are uniformly distributed on the entire 2-in wafer, and the current-voltage curve was measured from the device of an average level. It is found that the forward voltages (dynamic resistances) of the LED samples A, B, and C are 3.36 V (18.5 Ω), 3.27 V (16.9 Ω), and 3.19 V (14.0 Ω) under an injection current of 20 mA, respectively. The forward voltage of the LED sample B is lower than that of the LED sample A. This could be due to the high activation efficiency of Mg dopant in the p-type GaN layer during the thermal annealing in O2 ambient [11]. The results also show that the forward voltage and dynamic resistance of the LED sample C without pre-activation of the p-type GaN are the lowest in these devices, which prove that the p-type GaN was effectively activated during the fabrication process. It is generally believed that the activation temperature of p-type GaN in N2 ambient should be higher than 700°C to dissociate the Mg-H complexes. However, in our circumstances, the p-type GaN in LED sample C was activated at a relatively low temperature of 500°C in N2 ambient. We consider that this is attributed to the covered ITO film. The mechanism of activation of p-type GaN at a relatively low temperature in N2 ambient will be discussed later.Figure 2


Fabrication and characterization of GaN-based light-emitting diodes without pre-activation of p-type GaN.

Hu XL, Wang H, Zhang XC - Nanoscale Res Lett (2015)

Current-voltage and dynamic resistance characteristics of the LED samples A, B, and C, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385135&req=5

Fig2: Current-voltage and dynamic resistance characteristics of the LED samples A, B, and C, respectively.
Mentions: Figure 2 shows the current-voltage and dynamic resistance characteristics of the LED samples A, B, and C. The forward voltage is the average value of 100 LED chips which are uniformly distributed on the entire 2-in wafer, and the current-voltage curve was measured from the device of an average level. It is found that the forward voltages (dynamic resistances) of the LED samples A, B, and C are 3.36 V (18.5 Ω), 3.27 V (16.9 Ω), and 3.19 V (14.0 Ω) under an injection current of 20 mA, respectively. The forward voltage of the LED sample B is lower than that of the LED sample A. This could be due to the high activation efficiency of Mg dopant in the p-type GaN layer during the thermal annealing in O2 ambient [11]. The results also show that the forward voltage and dynamic resistance of the LED sample C without pre-activation of the p-type GaN are the lowest in these devices, which prove that the p-type GaN was effectively activated during the fabrication process. It is generally believed that the activation temperature of p-type GaN in N2 ambient should be higher than 700°C to dissociate the Mg-H complexes. However, in our circumstances, the p-type GaN in LED sample C was activated at a relatively low temperature of 500°C in N2 ambient. We consider that this is attributed to the covered ITO film. The mechanism of activation of p-type GaN at a relatively low temperature in N2 ambient will be discussed later.Figure 2

Bottom Line: During the fabrication process, a 100-nm-thick indium tin oxide film was served as the p-type contact layer and annealed at 500°C in N2 ambient for 20 min to increase its transparency as well as to activate the p-type GaN.We discussed the mechanism of activation of p-type GaN at 500°C in N2 ambient.Furthermore, x-ray photoemission spectroscopy examinations were carried out to study the improved electrical performances of the LEDs without pre-activation of p-type GaN.

View Article: PubMed Central - PubMed

Affiliation: Engineering Research Center for Optoelectronics of Guangdong Province, School of Physics and Optoelectronics, South China University of Technology, Guangzhou, Guangdong 510640 China.

ABSTRACT
We fabricated GaN-based light-emitting diodes (LEDs) without pre-activation of p-type GaN. During the fabrication process, a 100-nm-thick indium tin oxide film was served as the p-type contact layer and annealed at 500°C in N2 ambient for 20 min to increase its transparency as well as to activate the p-type GaN. The electrical measurements showed that the LEDs were featured by a lower forward voltage and higher wall-plug efficiency in comparison with LEDs using pre-activation of p-type GaN. We discussed the mechanism of activation of p-type GaN at 500°C in N2 ambient. Furthermore, x-ray photoemission spectroscopy examinations were carried out to study the improved electrical performances of the LEDs without pre-activation of p-type GaN.

No MeSH data available.