Geiger-mode focal plane array with monolithically integrated resistors
An image sensing device including a Geiger-mode avalanche photodiode (GmAPD), a read out integrated circuit (ROIC), and a limit resistor connected to the GmAPD and the ROIC in series, wherein the ROIC includes an active quenching circuit.
1 . An image sensing device comprising: a Geiger-mode avalanche photodiode (GmAPD);
a read out integrated circuit (ROIC); and
a limit resistor connected to the GmAPD and the ROIC in series,
wherein the ROIC includes an active quenching circuit.
2 . The device of claim 1 , wherein the GmAPD, the ROIC and the limit resistor compose one pixel, and
wherein the limit resistor is integrated in one pixel.
3 . The device of claim 2 , wherein the limit resistor is coupled between the GmAPD and the ROIC within one pixel.
4 . The device of claim 1 , wherein the limit resistor is configured to limit a magnitude of a GmAPD avalanche current before entering the ROIC.
5 . The device of claim 2 , wherein the limit resistor is monolithically integrated with the GmAPD of one pixel.
6 . The device of claim 2 , wherein the limit resistor is monolithically integrated with the ROIC of one pixel.
7 . The device of claim 1 , wherein the limit resistor is a thin-film resistor.
8 . The device of claim 1 , wherein the limit resistor comprises materials selected from the group consisting of NiCr and TaN.
9 . The device of claim 1 , wherein the limit resistor has a resistance in the range of about 1 kOhm to about 100 kOhms.
10 . The device of claim 1 , wherein the GmAPD comprises:
an active region formed within APD device layers;
a passivation layer disposed on the APD device layers;
an electrical contact formed on a portion of the active region;
the limit resistor, wherein the limit resistor is disposed on the passivation layer and is in electrical communication with the electrical contact; and
a bond pad formed on at least a portion of the limit resistor.
11 . The device of claim 10 , wherein the limit resistor has a serpentine shape, and
wherein the serpentine shape comprises a predetermined number of resistor squares between the active region and the bond pad.
12 . The device of claim 11 , wherein the predetermined number of resistor squares corresponds to a desired tunable resistance of the limit resistor.
13 . The device of claim 1 , wherein the active quenching circuit comprises:
a sense transistor configured to receive the avalanche current from the limit resistor;
an arm transistor; and
a disarm transistor, and
wherein the sense, arm, and disarm transistors are configured to provide active-quenching functionality for the GmAPD.
14 . The device of claim 13 , wherein the limit resistor is electrically coupled between an electrical contact of the GmAPD and an input of the sense transistor in the active quenching circuit within the ROIC.
15 . The device of claim 13 , wherein the active quenching circuit is configured to, in response to detecting an avalanche current, turn on the disarm transistor to reduce a voltage drop across the GmAPD.
16 . The device of claim 15 , wherein the active quenching circuit is further configured to:
detect a level of the voltage drop across the GmAPD falling to a level below a predetermined threshold voltage, and
in response to detecting the voltage drop across the GmAPD, turn on the arm transistor to re-arm the GmAPD.
17 . The device of claim 16 , wherein the predetermine threshold voltage corresponds to the breakdown voltage of the GmAPD.