Research Of Electrostatic Characteristics On GaN/Si Blue LEDs

GaN is a direct bandgap semiconductor, has attained great achievement in semiconductor field due to its excellent physical and chemical properties, and has been applied in information display, solid lighting and photoelectron devices. GaN/ Si is probable to integrate with conventional Si microelectronics, has low cost, and can be helpful to solve the luminescence problem of Si. Recent years, GaN-based material on Si substrate has made prodigious progress. However, it has certain distance in comparison with LEDs on sapphire substrate. So, it is necessary to study deeply.In this dissertation, photoelectric and electrostatic discharge properties of GaN-based blue LEDs on Si substrate after aging at 500mA direct current are studied. Some significant and innovative results achieved are as following:1. Photoelectric properties of GaN/Si blue LED chips with different etching depths are researched. Through accelerated aging experiment on testing board at 500mA current for these chips of 200μm×200μm before scribing, the results show that the chips with 0.8μm and 1.2μm etching depths have lower forward voltage and slower light decay in comparison with chips with 0.5μm; meanwhile, ESD is relatively steadier with aging time. Additionally, ESD of chips with 0.8μm etching depth is larger than the chips with 1.2μm.2. Photoelectric properties of GaN/Si blue LED chips with different substrate depths when transferring are studied. It is found that, in comparison with the chips of 200μm, these chips with 100μm depth have lower forward voltage, higher light intensity, slower light degradation and better electrostatic discharge. That maybe attributes to the native characteristics of Si.3. SiO₂ or SiN_x passivation layer is deposited on GaN/Si blue LED chips. The performance of the chips with SiO₂ inclines to stabilization and light intensity of the chips with SiN_x layer depresses severely.4. During the course of accelerated aging at 500mA current, electrostatic discharge of these chips descends and then ascends. Besides, along with time of aging, the curve has a forfication and has two trends. The same phenomenon is found in the encapsulated diodes during the aging under driven current at 30mA, 40mA, 50mA and 70mA. For the phenomenon that electrostatic discharge descends to 500V at the beginning, it is obtained that the time of appearencing the forfication needed is related and exponential with the aging current.5. If the chips maintained in the reverse current of 10μA for some time, both the corresponding reverse voltage and electrostatic discharge will be affected. Encapsulated LEDs have the same result. When maintained 2.5min, the time to have the forfication will be delayed.6. With ESD stroking on the encapsulated LEDs at 500V, 1000V, 2000V, 3000V, 4000V and 5000V, when aging at 30mA current, it is indicated that optical properties doesn’t have evident difference compared those without ESD.The dissertation was supported by 863-Project of China and Electronic Development Foundation in China.