Answer Happy

Question 3 (25 marks) A postgraduate research student, Francis, tries to use indium gallium nitride (InxGal-xN) to make a homojunction laser diode composed of a degenerate p-type and n-type regions. (a). Francis learned from somewhere that the In-Ga₁-xN has a band-gap energy of 2.38 eV. Calculate the expected emission wavelength of such a homojunction InGaN laser diode. (4 marks) (b). In his measurements, Francis finds out that the threshold current of the homojunction laser diode is 200 mA with the forward-bias voltage of 6.5 V. Sketch a graph showing the emission spectra of the InGaN laser diode when the forward-bias current is 100 mA and 400 mA respectively. All axes and key features of the curves must be labelled properly. (8 marks) (c). On one day, Francis mistakenly connected the p-type region to ground and the n-type region to 6.5 V. He failed to measure any optical output power from the laser diode. Sketch the energy