Michal Bockowski
Institute of High Pressure Physics Polish Academy of Sciences

Technologies of Gallium Nitride Crystal Growth in Poland

Location: EB1 Room 1011

Friday, August 23rd 2013 - 11:00 am

Polish technologies of gallium nitride (GaN) crystal growth as well as electronic and optoelectronic devices based on GaN substrates will be presented. Three crystallization techniques: i/ High Nitrogen Pressure Solution (HNPS) growth; ii/ Hydride Vapor Phase Epitaxy (HVPE); iii/ ammonothermal (Am) growth; and their combinations will be discussed.

Lecture will start from description of the HNPS growth. After basics of this method, its thermodynamic and kinetic aspects will be presented. Spontaneously grown HNPS-GaN platelets and needles will be briefly characterized. The next part will be focused on a seeded crystallization under pressure. Relatively new approach of seeded growth, multi-feed seed (MFS) configuration, will be described. This configuration is based on the conversion of free-standing HVPE-GaN crystals to the free-standing, pressure grown HNPS-GaN of much higher quality than the seeds. Highly conductive (n=5x1019 cm-3) and semi-insulating (?>1012 ?.cm) HNPS-GaN crystals and substrates prepared from them will be demonstrated and characterized.

For preparing the HVPE-GaN crystals, the seeds for the HNPS growth, homemade, horizontal, quartz HVPE reactor is used. 2 in. and up to 1 mm thick free standing HVPE-GaN can be obtained by growth on MOCVD-GaN/sapphire templates. Structural properties of this HVPE-GaN will be discussed.

Real challenge of the HVPE growth is, however, crystallization on ammonothermally grown, structurally perfect, GaN seed crystals. The properties of seeds as well as the initial growth conditions for HVPE crystallization will be described. Smooth GaN layers up to 2.5 mm thick (crystallized with a stable growth rate of 250 ?m/h) and of excellent crystalline quality, without cracks, and with low dislocation density (5x104 cm-2) will be presented. Preparation of the free-standing HVPE-GaN crystals by slicing and structural and optical quality of the resulting wafers will be discussed.

Technology of making UV/blue lasers diodes and high electron mobility transistors (HEMT) based on MOCVD and MBE growth on HNPS-GaN, HVPE-GaN and Am-GaN substrates will be briefly demonstrated at the end of this lecture.

North Carolina State University