Lumileds LLC

Lumileds Singapore Pte. Ltd.

Antonio Lopez Julia

Zhi Hua Song

Ronald Johannes Bonne

Nicola Bettina Pfeffer

Oleg Borisovich Shchekin

Yu-Chen Shen

Florent Monestier

Jeffrey DiMaria

A structure and method of micro-LEDs are described. The micro-LEDs have a GaN semiconductor structure containing a multi-quantum well active region configured to emit light of a visible wavelength range and a multilayer reflector structure that includes a distributed Bragg reflector (DBR) with a maximum reflectance at the visible wavelength range and to reflect the light emitted by the active region towards an emission surface of the semiconductor structure. The multilayer reflector structure also has a protective layer between the DBR and the GaN structure that is transparent to light of visible wavelengths. The multilayer reflector structure also has an absorbing metal layer that absorbs the light of visible wavelengths. A conductive material provides electrically contact to the semiconductor structure.

Narrowband reflector for micro-LED arrays

A light-emitting diode (LED) die can include a p-n junction between a p-doped semiconductor material and an n-doped semiconductor material. The LED die can include vias that can electrically power the p-n junction. The vias can optionally be electrically connected in parallel to one another. A controller can supply current to the vias to electrically power the LED die. The vias can be distributed with a density that peaks at or near a center of the LED die and decreases with increasing distances away from the peak of the density, such that when the vias are electrically powered, the LED die emits light with a surface luminance that peaks at or near the center of the LED die and decreases with increasing distances away from the peak of the surface luminance.

LED die having centrally peaked surface luminance

A micro light emitting diode (LED) die can include a matrix of micro LEDs with a variety of forward voltages. A method of reducing a number of undriven or under driven uLEDs can include providing, by a power supply, an alternating current voltage (V) with a minimum voltage (V) and a maximum voltage (V), Vbeing sufficient to drive a plurality of micro light emitting diodes (uLEDs) of a uLED die using a plurality of uLED drivers, identifying, by a controller coupled to the uLED drivers, a uLED of the plurality of uLEDs with a forward voltage (V) greater than V, and altering, by the controller, a time of a rising edge of a pulse width modulation (PWM)-on time of the uLED such that Vof the uLED is less than Vfor the PWM-on time.

Voltage supply amplitude modulation driving outlier microLEDs

A control system for an LED array relies on defining a first and a second group of separately addressed LED pixels, with the first group including pixels with an average current no less than the current at a Q point and a second group including pixels with an average current less than the current at a Q point. An amplitude signal provided to the first group of separately addressed LED pixels is selectively modulated, while providing a DC mode 100% duty cycle. An amplitude signal provided to the second group of separately addressed LED pixels is fixed, and a modulated duty cycle is provided.

Micro-LED amplitude control system

Discussed herein are systems, devices, methods, and computer-readable media for reducing a number of undriven or underdriven uLEDs of a uLED die. A method can include identifying, by a controller of a micro light emitting diode (uLED) die, a dynamic series resistance (R) or forward voltage (V) of a uLED of the uLED die, selecting, by the controller and based on the identified Ror V, a current level (I) less than a maximum current level (I) supplied by a uLED driver coupled to the uLED die, and causing, by the controller, current, at the selected current level, to be supplied to the uLED driver.

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Vaals, Netherlands

Antonio Lopez Julia