Ultracompact display pixels: Tunnel junction nanowire photonic crystal laser

Visual reality (VR) and augmented reality (AR) displays require ultra-high definition pixels with smaller sizes, narrower pitches and vertical beam angles. Unfortunately, micro-LED devices have an insurmountable challenge in reducing the pixel pitch due to the wide divergence angle of light source. Alternatively, a vertical-cavity surface-emitting laser is emerging as the most promising candidate for future high-definition display applications. Here, we have shown the world's first display implementation using an electrically injected DBR-free surface-emitting photonic crystal laser. We have also introduced, for the first time, a tunnel junction nanowire structure in the surface emitting photonic crystal laser system. With use of the tunnel junction, highly resistive p-GaN/metal contact was completely removed. The photonic crystal effect by photonic band edge mode eliminated the use of DBRs, which is essential for laser devices. We have further demonstrated that the spectral linewidth can be readily scalable by controlling the spacing of nanowires. Moreover, it was confirmed that such scalable spectral linewidths remain virtually invariant under the different temperature range of 12–375 K, which are critical to color accuracy in display. An ultra-compact micro-display with a pitch of 10 µm and a pixel size of 4 µm² was realized by electrically injected DBR-free surface-emitting photonic crystal laser devices.