First optical method for studying structural and electronic properties of GaN and GaN composites at the nanometer scale

The Fraunhofer Institute for Laser Technology ILT working closely with RWTH Aachen University's Institute of Physics (IA) has developed an analysis technology that, for the first time, allows the structural and electronic properties of GaN and GaN composites to be studied optically on the nanometer level.

The resolution of conventional optical microscopes reaches its physical limits when confronted with objects on the nanometer scale. Because of the light source employed, structures in the nanometer range cannot be brought into focus. Near-field microscopy circumvents this limitation and penetrates the nanometer domain to provide an optical view. But this places extremely high demands on the light source used.

With fellow researchers from the Chair for Experimental Physics at RWTH Aachen University, scientists from Fraunhofer ILT have spent the past few years developing an innovative, broadband tunable laser system that is geared toward the particular requirements of semiconductor analysis at the nanometer level.

Wavelength can be adjusted to the material under inspection, which enables the new system to investigate a wide range of materials. In contrast to the solutions available on the market to date and those employed in research and development, the new system from Aachen provides the means for much faster spectroscopic analyses. It has also opened up access to material systems that were beyond the capacities of previous systems. This includes GaN and GaN composites.

Using the new analysis system, last year the researchers in Aachen were able to obtain an optical 2D image showing tensions in the crystal structure of undoped GaN wafers for the very first time. Computer simulations helped quantify the exact extent of the tension. Recently the technique was also applied to a variety of doped GaN layers within complex structures. It's the first time an optical technique has been available to study the structural and electronic properties of GaN and GaN composites on the nanometer scale. (Pictured above is a near field microscope with a fragment of GaN wafer.)

Cost-effective, precise and non-destructive

Near-field microscopy offers cost and quality benefits over standard analysis techniques. The structural properties of thin GaN layers are currently studied using transmission electron microscopy; however, the costs incurred are extremely high, due in part to the laborious sample preparation process. Near-field analysis can usually be conducted without any preparation.

Another benefit concerns secondary ion mass spectrometry, which is used to study the electronic properties. Although this technique can be used to determine electronic properties along an axis at the nanometer level, it isn't yet possible to laterally ascertain the concentration of doping atoms at a comparable resolution. The technique also damages the samples.

In contrast, near-field microscopy offers nanometer-scale resolution in all dimensions. It is a completely non-destructive technique and can be implemented under normal conditions.

Potential applications for the analysis system

Near-field microscopy is suitable for a range of applications. When used in close consultation with the developers of new semiconductor components, for instance, the method can help optimize process parameters in a targeted way. The analysis also aids in the understanding of physical processes from a very early stage in development, particularly at the interfaces between the individual layers. 

These findings can shape subsequent development stages significantly. In high-frequency and power electronics, too, GaN is becoming more and more common as a component due to its physical properties. Near-field microscopic analysis techniques are ideally suited for researching these materials. 

AngelTech Live III: Join us on 12 April 2021!

AngelTech Live III will be broadcast on 12 April 2021, 10am BST, rebroadcast on 14 April (10am CTT) and 16 April (10am PST) and will feature online versions of the market-leading physical events: CS International and PIC International PLUS a brand new Silicon Semiconductor International Track!

Thanks to the great diversity of the semiconductor industry, we are always chasing new markets and developing a range of exciting technologies.

2021 is no different. Over the last few months interest in deep-UV LEDs has rocketed, due to its capability to disinfect and sanitise areas and combat Covid-19. We shall consider a roadmap for this device, along with technologies for boosting its output.

We shall also look at microLEDs, a display with many wonderful attributes, identifying processes for handling the mass transfer of tiny emitters that hold the key to commercialisation of this technology.

We shall also discuss electrification of transportation, underpinned by wide bandgap power electronics and supported by blue lasers that are ideal for processing copper.

Additional areas we will cover include the development of GaN ICs, to improve the reach of power electronics; the great strides that have been made with gallium oxide; and a look at new materials, such as cubic GaN and AlScN.

Having attracted 1500 delegates over the last 2 online summits, the 3rd event promises to be even bigger and better – with 3 interactive sessions over 1 day and will once again prove to be a key event across the semiconductor and photonic integrated circuits calendar.

So make sure you sign up today and discover the latest cutting edge developments across the compound semiconductor and integrated photonics value chain.

REGISTER FOR FREE

VIEW SESSIONS