The trend of electronic device miniaturization, from the micro-scale to the nano-scale, presents a temperature measurement challenge. The available techniques have limitations in terms of either resolution, calibration, acquisition time or equipment cost. Here we demonstrate a thermography technique called hyperspectral quantum rod thermal imaging (HQTI), which exploits temperature dependent photoluminescence (PL) emission of quantum rods to obtain the surface temperature map of a biased electronic device, with a straight-forward calibration. This method uses relatively simple, low cost equipment, while achieving submicron spatial resolution. This technique is demonstrated by measuring the thermal map of a direct current (DC) operated Gallium Nitride (GaN) high electron mobility transistor (HEMT), achieving a temperature precision of ~4 oC, and a ~700-800 nm estimated lateral optical resolution. This is a versatile method for both measurement in sub-micron scale regions of interest and of larger areas in the hundreds of micrometers range.