An alternative to silicon: scientists overcome obstacles in creating gallium oxide semiconductors

Japanese researchers from the Nagoya University solved technological difficulties, using gallium oxide (Ga₂O₃) in semiconductors. 

Gallium oxide is a promising material, can make electronic devices much more energy efficient, than those, based on silicon. For the correct operation of electronic diodes, 2 types of semiconductor layer are required — layers of negative polarity (n-type) and layers with positive polarity (p-type). 

Scientists have managed to create reliable layers of gallium oxide (n-type), but the creation of p-type layers was difficult, because the crystal structure of gallium oxide naturally prevents the penetration of atoms, necessary for the formation of these layers. Because of this, gallium oxide-based semiconductors had poor performance and were unreliable. 

Japanese researchers have created the first functional pn-diodes, based on gallium oxide. Their method allows use gallium oxide to create advanced semiconductors and energy-efficient devices. In addition, the innovative pn diodes are capable of transmitting twice as much electric current as previous Ga₂O₃-based diodes. 

Pn diodes are made by combining p- and n-type semiconductors. This creates a junction point, that controls the electric current. Such diodes can withstand high voltages and are suitable for most electronic devices. However, existing Pn diodes waste a lot of energy in the form of heat, especially in energy-intensive applications, such as electric cars and renewable energy sources. 

Gallium oxide-based Pn diodes can withstand twice the current generation of previous gallium oxide devices and consume less power than silicon diodes. This makes these diodes ideal for demanding devices and applications and reduces the requirements for cooling systems, improves energy efficiency in powerful systems and reduces operating costs. 

The problem was that the crystal structure of gallium oxide readily accepted the atoms, needed to create the n-layers, and rejected the atoms, needed to create p-layers. Without both types working together, gallium oxide remained limited in practical application.

To solve this problem, japanese researchers have introduced atoms nickel into the gallium oxide layer by injection. They bombarded the surface of the material with individual atoms at high speed. After that, the material was heated twice, first to a temperature of 300°C with activated oxygen radicals (with oxygen atoms that have been energized by a patented plasma treatment), and then — to a temperature of 950°C in an oxygen environment. This led to the transformation of nickel into nickel oxide and its complete integration with the crystal structure of gallium oxide.

The results of the study are published in the journal Journal of Applied Physics

Source: TechXplore