GaN and related III-nitrides find great application in optoelectronic devices like light-emitting diodes (LEDs) and hence there is an increase in their demand. Although sapphire is still considered to be the most apte substrate for the growth of GaN based LEDs, but it is certainly not the most ideal one due to its low thermal conductivity and a large lattice mismatch with GaN. Hence, for the production of high performance and highpower LEDs, sapphire is being substituted by unconventional substrates having low lattice mismatch with GaN and a relatively larger thermal conductivity. The work focuses on the performance of such GaN-based LED materials and devices on unconventional substrates. It involves the detailing of the reasons responsible for the difficulty in developing GaN-based LEDs on the unconventional substrates. The solutions to outdo these difficulties and enhance the III-nitride growth are also elaborated along with the defect control, and chip processing for each type of unconventional substrate. The techniques developed to achieve such highperformance GaN LEDs are also discussed. With this it becomes quite easy to study the progress made in this particular field of physics. We strongly believe that with constant efforts in this field the quality of GaN based LEDs on unconventional substrates can improve progressively. And in the near future, with the usage of such unconventional substrates, we can produce LEDs commercially with a varied set of applications. © 2018 SPIE.