Correct oven temperature for chicken tikka at home
Make sure that the tikkas do not touch a surface e.g. an aluminium foil or a tray. Suspend them from a grid and use a lined tray at the bottom of the oven to collect the fat/juices. Cook at 180°C for 20-25 minutes (to cook the chicken through) and then cook on maximum temperature (usually 350°C) for 5-7 minutes to get the charred/burnt effect. 

As a side note, roast some besan (gram flour) and ajwain (carom seeds) in 1 tablespoon of mustard oil and add it to the marinade. And sprinkle coriander and mint extremely finely chopped together over your chicken immediately after it is out of the oven.  

For the best tikkas or tandoori, if you have the time and space, build and use your own tandoor as described here: https://www.youtube.com/watch?v=8Ukb_WoUG2Q