Improvement of Blue Llight-Ight-ight-eeemitting Mitting Ddiodes Iodes with an Undoped Graded Layer As the Electrons Tunneling Barrier Layer

The advantages of blue light-emitting diodes with an undoped AlxGa1-xN graded layer (x graded from 0.1 to 0) worked as electrons tunneling barrier layer are studied numerically. The energy band diagrams, carrier concentrations, output power, radiative recombination rate and internal quantum efficiency are investigated by using the Crosslight simulation programs. The simulation results show that the structure with a AlGaN graded electron tunneling barrier layer has better performance over the common one, which can be attributed to the significantly increased hole concentration resulting from the pinning effects and the barrier for electrons injection caused by the graded layer. Therefore, the efficiency of hole injection is improved, with which both the IQE and the total lighting power are increased.