We have determined thermal stability of various InGaN laser diodes emitting in the spectral range of 390-436 nm. Their characteristic temperature T-0 increases steeply with the increasing emission wavelength, reaching the value of around 230 K. Our analysis of current-light characteristics and activation energy of electroluminescence proves that this behavior is predominantly related to the thermal escape of electrons from quantum wells, which depends critically on their depth. (C) 2013 AIP Publishing LLC.