• Johnny Dahl

The importance of III-V materials interface quality and how Kontrox™ helps to improve it

Compound semiconductor materials have been around us for quite a few years already, and despite of their overwhelming and superior characteristics compared to those of the almighty silicon, their market share has been rather small (approximately 10%) mainly dictated by the cost and the difficulty of their processing. This trend is now changing, the compound semiconductor market is growing faster than ever driven by new technology sectors where the technical requirements are extremely more demanding and that cannot be easily met by Silicon based devices, such as power electronics for electrical vehicles, power amplifiers for 5G communications, lasers and sensors for LIDAR and VR/AR devices.

It is well understood that the quality of the material surfaces and interfaces play a crucial role in electronic and photonic semiconductor devices.

Devices manufactured from compound semiconductors, more precisely from III-V materials, typically present an epitaxial stack of different III-V materials and often terminated with some overcoating or dielectric films. In such a stack, the interface between two semiconductors usually has a very low defect density due to the crystalline nature of the interface achieved during the epitaxial growth, however, interfaces where a III-V material is exposed to air or in contact with a dielectric material, which usually is some kind of oxide, are full of defects as a result of the aggressive and amorphous oxidation of the III-V´s. The low quality of those interfaces has hampered the utilization of compound semiconductors since the beginning. One of the fundamental problems inherent to the III-V materials is that they react very strongly with oxygen from air or during dielectric deposition creating a disordered structure with lots of electronic states in the band gap. These defect states cause many harmful effects such as leakage current, loss of efficiency, reliability issues and manufacturing yield losses. These problems combined with the more exigent operational demands creates an urgent demand from the market for better III-V surface passivation methods.

Our company has developed a novel technology based on precise material surface reconstruction techniques resulting in new crystalline stable surface structures that have a passivating effect on a big variety of III-V materials. This enables the manufacturing of material interfaces with unprecedented low level of defects and high quality thus facilitating the desired increase of efficiency. The new technology of Comptek Solutions circumvents the problem of disordered interfaces by inducing surface reconstructions and creating an oxygen-containing crystalline layer on the III-V material by reorganizing the III-V surface at atomic scale.

Comptek achieves the crystalline oxide structure by, firstly functionalizing the material surface in a very controlled environment. The surface then is forced to undergo a transformation into a new surface reconstruction. This oxygen-induced surface reconstruction is inert to subsequent oxygen exposure, creating new possibilities in the fields of photonics, analog electronics and digital electronics.

For some materials the measured surface states defect density has been 98% lower than those obtained by industry standard passivation methods, which implies a tremendous improvement in the device electrical behaviour. The improvement can be attributed to the stability of the surface reconstruction, which maintains long range periodicity even during dielectric deposition process.

Our technology is a notably different approach when compared to traditional methods where protective materials or overcoating are deposited onto the surface. One practical example is the deposition of crystalline gadolinium-gallium-oxide insulators on a III-V based capacitor or MOSFET structure, where the target III-V surface does not contain oxygen and therefore an unavoidable reaction happens between the oxide molecules and the III-V material creating disorder and amorphous structure in the interface.

Some application examples of this technology are transistor application, where the quality of the interface between gate dielectric and III-V channel material can be increased dramatically, obtaining much better output levels. In optoelectronic devices, the effective passivation of surfaces and MESA side walls can enhance the performance of photodetectors, LEDs or lasers.

Comptek Solutions can tailor the technology to be implemented to customers devices and materials, helping them to achieve device improvements and also manufacturing yield increases. For more information, contact us at info@comptek-solutions.com

#iiivpassivation #Kontrox #oxidation


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