Przewodzące struktury GaN/AlGaN/SiC do konstrukcji nowych generacji elektronicznych przyrządów wertykalnych

Electronic devices (transistors, LEDs, laser diodes, p-i-n diodes) based on AlN-GaN-InN nitride semiconductors create huge mass and niche markets, however, compared to other semiconductors (Si-Ge, AlAs-GaAs-InAs-AlP-GaP-InP) their technology is much more difficult due to the lack of lattice-matched cheap and large substrates for epitaxy. The most popular approach is to use foreign substrates: Si and sapphire with a lattice mismatch to GaN of over 15%, relaxed by a very high dislocation density (over 10^8cm-2). These two foreign substrates are extremely cheap (below 1 Eur per cm2) and are produced as discs with diameters of 20 cm. All white LEDs and a large part of nitride transistors are grown on such substrates. However, many nitride devices (laser diodes, vertical transistors) require much lower dislocation densities and then GaN substrates are used. Their technology is, however, extremely difficult and therefore their price is very high (approx. 200 EUR/cm2), and the typical diameter is 5 cm (10 cm diameter discs are slowly being introduced). In the case of devices based on AlGaN with a high Al content (e.g. UV emitters), even more expensive AlN substrates are used. Silicon carbide is a substrate that is a compromise between cheap and large foreign substrates (sapphire, Si) giving a very high dislocation density in AlGaInN layers and small and expensive GaN, AlN substrates with low dislocation density. SiC has a lattice mismatch to GaN (3.5%) and to AlN (1%) much smaller than silicon and sapphire, therefore the dislocation density in AlGaInN layers on SiC can be at the level of 10^6cm-2. The price of the conductive SiC substrate is 10 times lower than that of GaN substrates, and additionally, these substrates are currently produced as discs with a diameter of 15 cm and 20 cm. The best and most expensive electronic devices are and will be produced on GaN and AlN substrates, mass and cheapest devices on Si and sapphire substrates, while a great many devices could be grown on SiC substrates. However, these substrates have one fundamental disadvantage, which makes it impossible to make any vertical devices in which the current flows from top to bottom. This disadvantage results from the current technology of applying AlGaInN layers to SiC. Namely, these layers are preceded by an AlN buffer, which has the smallest lattice mismatch to SiC. This buffer is completely insulating, which prevents vertical current flow. In the proposed Project, we will develop a technology for making a conductive buffer AlGaN:Si on a SiC substrate. For this purpose, we will optimize the growth conditions in the MOVPE (metalorganic chemical vapor phase epitaxy) reactor of such a buffer, and in particular, we will select the flows of reagents, growth temperature and pressure, and disorientation of SiC substrates. The goal of the optimization will be good electrical conductivity of the buffer and the lowest possible dislocation density in the GaN layer grown on the AlGaN:Si buffer. The developed technology will enable the production of epitaxial device structures (vertical transistors, p-i-n diodes, but also laser diodes and others) on SiC, significantly expanding the offer of the Project Applicant, SEEN Semiconductors.