A client had an issue with their InGaN LED regrowth process. The initial work showed very poor regrowth quality, despite working to implement surface cleaning processes. Cross-sectional SEM analysis showed a high concentration of defects originating at the interface and persisting during the LED growth:

The resulting I-V results showed a resistor parallel with a diode, where the excess defects led to the parasitic resistor. Alongside the I-V results, the EL results showed little to no light output.

From this starting point, an in-depth literature review assessed the latest techniques on InGaN LED regrowth and surface treatments. The likelihood of issues, despite a clean interface, was a high-powered dry etch which led to crystal damage. GaN is a material with a high-energy bond which is often etched in Cl2 and Ar-based dry etch, where high forward power is leveraged for a reasonable etch rate alongside a high degree of anisotropy. Unfortunately, this high-powered etch leads to subsurface crystal damage, impeding regrowth quality. A multi-step high-to-low powered dry etch was developed, along with a chemical surface treatment to provide an atomically prestine surface. Upon regrowth with this new process, the regrown InGaN LED shows a clean interface:

With the clean interface, I-V data is compared:

The I-V results show conventional characteristics for an InGaN LED, with comparable leakage to a conventionally grown LED with no regrowth. EL results indicate a high level of LED brightness, matching the I-V data. The new process flow is now being implemented by the client for future regrowth experiments and products.

A facility had issues with their Atomic Layer Deposition (ALD) tool. The issue led to very poor breakdown results, such that an SiO2 film 20nm thick would break down often with just the application of a few volts across it. A great way to gauge initial oxide quality is to test the breakdown of capacitors by ramping the voltage and recording the breakdown voltage. When plotting cumulative percent failure of capacors vs the voltage a plot should be generated similar to figure below:

Two populations can be observed; an intrinsic one, where the voltages fail around a higher voltage window, and an extrinsic population, where a few capacitors fail at lower voltages and form an extended curve. The intrinsic population is a gauge of the material quality of the oxide, while often the extrinsic population is due to external defects such as particles that thin the oxide.

Upon fabricating test capacitors with the suspect ALD oxide and performing the same type of breakdown testing, it was found that there was no delineation between extrinsic and intrinsic, which indicates incredibly poor native material quality:

With further investigation and working with the tool vendor, it was found that several parameters were incorrectly used, leading to the poor oxide quality.