200-mm GaN-on-Si Based Blue Light-Emitting Diode Wafer with High Emission Uniformity

Abstract

We investigated the emission wavelength uniformity of 200-mm GaN-on-Si based blue light-emitting diode (LED) wafer grown by metalorganic vapor phase epitaxy (MOVPE). The larger the Si substrate diameter becomes, the more difficult to obtain uniform distribution of the emission wavelength because of the larger bow during growth, resulting in larger on-wafer inhomogeneity in growth temperature. Owing to the GaN-on-Si buffer strain management, optimized gas flow condition, and precise control of temperature balance in a reactor, we have achieved high thickness and crystal quality uniformity over the 200-mm GaN-on-Si based blue LED wafer. As a result, excellent blue photoluminescence emission wavelength uniformity from the InGaN-multi-quantum wells can be demonstrated on a 200-mm wafer with a standard deviation of 2.53 nm (0.57%). Less wavelengths binning with these highly uniform emission over the 200-mm wafer show the capability of sustainable cost reduction in LED fabrication based on GaN-on-Si technology.

Demonstration of novel high-efficiency blue LEDs on silicon substrates

“…3 Many groups have attempted to tackle this issue and have reported improvements in the manufacture of GaN-based LEDs. 4,5 For example, gas flow conditions and precise control of temperature in a reactor have been optimized. 5 In addition, we have previously developed LEDs with low threading dislocation densities (TDDs), i.e., of less than 2 10 8 cm 2 on Si (111 crystallographic plane) substrates.…”

“…4,5 For example, gas flow conditions and precise control of temperature in a reactor have been optimized. 5 In addition, we have previously developed LEDs with low threading dislocation densities (TDDs), i.e., of less than 2 10 8 cm 2 on Si (111 crystallographic plane) substrates. 6,7 Those TDD values were almost the same as those of LEDs grown on Al 2 O 3 (0001) substrates.…”

Excellent uniformity on large diameter GaN on silicon LED wafer

“…High on-wafer uniformity on large area wafers contributes to cost reduction by reducing the binning overhead. Despite the severe challenges that the GaN growth on Si poses [2], crack free LED wafers on Si(111) substrates up to 200 mm have been demonstrated [3,4]. Even more impressive, the brightness values achieved by LEDs grown on Si have reached comparable values to sapphirebased devices as demonstrated by research samples and production devices as well [5,6].…”

Highly Uniform Electroluminescence from 150 and 200 mm GaN-on-Si-Based Blue Light-Emitting Diode Wafers

“…There also exists a large mismatch of thermal expansion coefficient (TEC) between Si and GaN (46%) that is responsible for wafer bow and cracking of the epitaxial layers during cooling down from the growth temperature. Despite these challenges, crack-free LED wafers on Si(111) up to 200 mm have been demonstrated 2,3) and the brightness gap between the novel GaN-on-Si and mature GaN-on-sapphire LED technologies has been bridged to a large extent. 4) AZZURRO Semiconductors has developed a proprietary buffer structure that allows a significantly reduced dislocation density in the LED active region by simultaneously compensating the lattice and thermal mismatch for GaN-on-Si wafers.…”

“…This results in superior wavelength and brightness uniformities over 150 and 200 mm LED wafers. 2) Using optimized processes, the wafer bow at room temperature can be controlled to values within and less than AE20 m for up to 200 mm wafers in production. The low bow value is essential for producing these wafers in standard Si production lines and avoiding cracking during wafer processing/ handling-or processing-induced nonuniformities that would also negatively affect the final yield.…”