Investigation of GaN-based Light-Emitting Diodes with AlN Film
|關鍵字:||氮化鋁;電流阻擋層;側壁鈍化層;電流散佈;AlN;Current blocking layer;Sidewall passivation layer;Current spreading|
In this study, we examined the characteristics for the application of AIN thin films on GaN light-emitting diode (LED) devices. The devices structure contained a current blocking layer (CBL) and a passivation layer. We also compared the differences in optical and electrical properties between this devices structure and devices that traditionally employing silicon dioxide thin films. We used the sputtering system to grow thin films. Transmittance measurements indicated that the AIN thin film had a transmittance of above 90% in the visible light region. Additionally, a developer was used to test the etch rate of the AIN thin films. The results of this test indicated that after heat treatment in a nitrogen atmosphere for 1 min, the resistance of the AIN thin film to the developer etching increased because of improvements in lattice quality. The experiments also confirmed the feasibility of employing AIN thin films in follow-up experiments on LED devices. Next, we used the AIN thin film as the CBL in the LED. First, current-voltage (I-V) curve indicated that AIN thin films had higher series resistance values compared to that of the silicon dioxide thin films. These values increased with increases in the thin-film thickness. With an AIN thickness of 1800 Å, the corresponding LED light output power with 20 mA injection increased by 8% compared to the conventional LED. The light output power increased because the CBL effectively reduced the probability of the current flowing through the area under the p-type electrode. This improved the phenomenon of the electrode masking the light. Next, we investigated the use of AIN thin films as the sidewall passivation layer for LED devices. Heat treatment experiments indicated that although the heat treatment process can reduce the leakage current in the components, it also reduces the LED’s light output power by approximately 9% compared to the conventional LED. The decrease in light output power was caused by a decline in the thin-film transmittance in the sidewall passivation layer area. Finally, we used the developer to remove the heat-treated AIN passivation layer. The light output power with 20 mA injection increased by approximately 11% compared to that of the conventional LED. The light output power increased because the resistivity of the ITO thin film located in the area surrounding the LED mesa increased and the sidewall resistance value changed. This caused the current to concentrate in the area not covered by the AIN thin film, generating an effect similar to that of the CBL. This effect improved the current spreading in the LED n-type electrode area.
|Appears in Collections:||Thesis|