an optoelectronic device includes a semiconductor substrate , having front and back sides and having at least one cavity extending from the back side through the semiconductor substrate into proximity with the front side . at least one optoelectronic emitter is formed on the front side of the semiconductor substrate in proximity with the at least one cavity . a heat - conducting material at least partially fills the at least one cavity and is configured to serve as a heat sink for the at least one optoelectronic emitter .