POET Technologies Inc.

It hard to imagine what configuration POET will use for such things as gesture recognition and image detection. When we talk about the POET detector it has some very significant attributes such as multispectral response. It has the capability of capturing multi spectral images…The ability to see through fog and haze. The CCD camera has vast improvements over silicon in sensitivity and speed. Even the VSEL has an added unique feature that allows for beam steering.

Some bits from one of the POET patents…some easy reading…lol:

The heterojunction-thyristor-based pixel element is suitable for many imaging applications, including CCD-based imaging arrays and active-pixel imaging arrays.

1. Field of the Invention

The present invention relates to optoelectronic devices. More particularly, the present invention relates to imaging arrays based on charged coupled devices (CCD) formed from semiconductors such as gallium arsenide (GaAs) which are capable of generating electrical signals in response to light. The invention is particularly applicable to the imaging and the telecommunications arts, although it is not limited thereto.

Silicon technology is limited by the presence of the silicon oxide in both the active and passive regions of the integrated circuit in a number of ways. A main limitation is the sensitivity of the oxide to radiation flux. The radiation creates traps and other charged defects in the insulator which alter the internal voltage thresholds in both active and passive regions within the integrated circuit. After a certain cumulative exposure level, these threshold changes render the circuit inoperable. The gate oxide creates limitations in other ways as well. The silicon CCD couples one pixel to the other via overlapping gates. Each overlapping gate creates a small region of thicker oxide between pixels which inhibits charge transfer and therefore sets a speed limitation upon the CCD. These oxide barriers are fundamental to the silicon CCD and constitute a transfer speed limitation. Some approaches have been employed to eliminate these effects such as the virtual phase CCD. However, these structures are then faced with barriers created by implant misalignment and a lack of well capacity. In any event the transfer speed in the silicon CCD rarely exceeds a few MHz.

A further limitation of the silicon CCD is its spectral sensitivity. The silicon CCD absorbs radiation across its energy gap and therefore is insensitive to radiation with a wavelength longer than about 1 um. It is also insensitive to ultraviolet (UV) radiation.

As disclosed in parent application U.S. Ser. No. 09/556,285, III-V device structures based upon GaAs substrates have the potential to overcome the above limitations. In particular, the GaAs CCD has the potential to absorb electromagnetic energy within a quantum well between the various subbands. This provides the GaAs device with unique capabilities of intersubband absorption and sensitivity in the mid wavelength infrared, long wavelength infrared and very long wavelength infrared regions. The GaAs device structures that currently perform the intersubband detector functions are the QWIP (quantum well infrared photodetector) devices. Two significant limitations of the QWIP as currently implemented are the existence of a significant level of dark current that necessitates cooling of the device to 77.degree. K., and the fact that the device is not compatible with GaAs integrated circuits. When originally demonstrated, the QWIP was considered advantageous because of its potential compatibility with GaAs integrated circuits. However, this compatibility has never been established and so present technology combines the GaAs QWIP wafer in a hybrid fashion with a Si read-out integrated circuit.

The imaging array of the present invention (and the signals produced therefrom) can be used in many applications. For example, it can be used to perform imaging operations over nanosecond to millisecond time increments (due to the high speed of response of the 2D gas). Moreover, it can readily be adapted to image wavelengths over a broad spectrum of wavelengths (including mid-infrared wavelengths as well as long-infrared wavelengths). Moreover, the imaging array of the present invention can be efficiently integrated with a broad range of optical and electronic devices, for example to provide an integrated array together with associated optoelectronics and/or logic circuits and/or signal processing circuits.