GaN‐Based Vertical‐Cavity‐Surface Emitting Lasers with Polarization‐Induced Interface Charges and Bulk Charges to Manage the Carrier Injection

Herein, Al‐composition gradient p‐type electron blocking layer (p‐EBL) is proposed and physical models are developed to investigate the impact of the proposed p‐EBL on carrier injection and stimulated radiative recombination for GaN‐based vertical‐cavity‐surface emitting lasers (VCSELs). The results show that when compared to VCSELs with constant Al‐composition p‐EBL, the Al‐composition gradient p‐EBL can effectively weaken polarization‐induced electric field at the last quantum well/p‐EBL interface. This can suppress the electron accumulation therein and reduce the electron leakage. However, it is also found that the Al‐composition gradient layer generates additional energy barrier for holes. Hence, the polarization‐induced negative bulk charges in the Al‐composition gradient layer strongly affect the hole injection. The polarization self‐screening effect shall be used to suppress the electric field in the Al‐composition gradient layer, so that the hole can gain more energy. This tunes Fermi‐Dirac distribution for holes and enables the holes to travel across the valence band barrier in the Al‐composition gradient layer.