CHARACTERISTICS OF INFRARED DETECTORS

This graph summarizes the wavelength response of some semi-

conductors used as detectors for infrared radiation. The quantity

D*(λ) is the signal to noise ratio for an incident radiant power den-

sity of 1 W/cm

2

and a bandwidth of 1 Hz (60° field of view). The

Ge, InAs, and InSb detectors are photovoltaics, while the HgCdTe

series are photoconductive devices. The cutoff wavelength of the

latter can be varied by adjusting the relative amounts of Hg, Cd,

and Te (three examples are shown at 77 K). The graph also shows

the theoretical background limited sensitivity for ideal detectors

which introduce no intrinsic noise.

Reference

Infrared Detectors 1995, EG&G Judson, Montgomeryville, PA.

10

14

10

13

10

12

10

11

10

10

10

9

10

8

D*(

λ)

1

2

3

4

5

6

7 8

10

12

20

30

Wavelength (

µm)

Ideal Photovoltaic

(BLIP Limit)

Ideal Photoconductor

(BLIP Limit)

Ge 77 K

Ge -30

°C

Ge 22

°C

InAs 22

°C

HgCdTe -75

°C

Doped Ge 4 K

HgCdTe 77 K

HgCdTe 77 K

HgCdTe -55

°C

HgCdTe 77 K

InSb 77 K

InAs 77 K

InAs -30

°C

10-244

Section 10.indb 244

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