High resolution electroluminescent display using active matrix approach

An approach to a high resolution display based on electroluminescent (EL) technology is developed. In this approach, a silicon wafer with integrated high-voltage EL drivers and low-voltage line drivers is used for the EL thin-film substrate. New approaches in circuit design and thin-film processing are developed in order to achieve an active matrix electroluminescent (AMEL) display providing the capability and flexibility required for various head-mounted display applications. A zener transistor concept is incorporated into the pixel design to allow for the achievement of a pixel pitch of 24 {dollar}mu{dollar}m. The EL processing is adjusted to allow for the use of IC processing already available in a commercial silicon foundry. These EL processing modifications include the use of atomic layer epitaxy (ALE) thin-films to achieve conformal coating requirements, modification of the EL thin-film stack structure to avoid thin-film stress problems, and changes in the process flow to allow for the use of Al conductors. Furthermore, to achieve the desired high brightness levels, the drive frequency is increased to about 5 kHz, from a typical value of 60 Hz. Brightness saturation problems associated with driving the AMEL device at such a high frequency are investigated and resolved. To achieve 64 levels of gray scale, a new digital gray scale approach is successfully incorporated into the display operation. The improvements are demonstrated in the realization of a 1280 x 1024 AMEL display.