CMOS-Controlled Color-Tunable Smart Display

Abstract

We demonstrate a color-tunable smart display system based on a micropixelated light-emitting diode <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(\mu\hbox{LED})$</tex></formula> array made from one InGaN epitaxial structure with high (0.4) indium mole fraction. When integrated with custom complementary metal–oxide–semiconductor (CMOS) electronics and a CMOS driving board with a field-programmable gate array (FPGA) configuration, this <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{LED}$</tex></formula> device is computer controllable via a simple USB interface and is capable of delivering programmable dynamic images with emission colors changeable from red to green by tailoring the current densities applied to the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{LED}$</tex></formula> pixels. The color tunability of this CMOS-controlled device is attributed to the competition between the screening of piezo-electric field and the band filling effect. Comparable brightness of the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{LED}$</tex></formula> pixels emitting at different colors was achieved by adjusting the duty cycle. Further measurement suggests that this microdisplay system can also be used for high-speed visible light communications.