Development of efficient, radiation-insensitive GaAs:Zn LEDs
A figure of merit for the radiation resistance of light-emitting diodes (LEDs) is the product of the pre-irradiation minority carrier lifetime, tau/sub 0/, and the damage constant, K. When the tau/sub 0/K product multiplied by the radiation fluence, PHI, gives a number comparable to 1.0, the LED will show significant degradation. Evidence in the literature suggests that tau/sub 0/K decreases with increasing p-type dopant concentration in the GaAs LEDs. This is further supported by measurements of diffusion length, L/sub n/, in GaAs as a function of dopant concentration. In Ge-doped p-type GaAs, L/sub n/ was constant with increasing Ge concentration, N/sub Ge/, up to N/sub Ge/ approximately 1 x 10/sup 18/ cm/sup -3/. However, above this concentration L/sub n/ was observed to decrease with increasing N/sub Ge/. This was attributed to a decrease in the radiative lifetime at large N/sub Ge/ concentrations. Below 10/sup 18/ cm/sup -3/, L/sub n/ was controlled by nonradiative centers, but above 10/sup 18/ cm/sup -3/ the radiative lifetime decreased to the point where it determined L/sub n/ and hence, tau/sub 0/. The evidence outlined above suggests an attractive method for radiation hardening GaAs LEDs. By heavily doping the p side of the LED one obtains a small value of tau/sub 0/ and hence a small tau/sub 0/K. In addition, the radiative efficiency increases giving greater light output. This is to be contrasted with radiation hardening of many types of Si devices in which shortening of the lifetime to achieve radiation resistance results in poorer device performance. Similar problems are expected with ternary LEDs, such as GaAlAs, in which tau/sub 0/K is small but the radiative efficiencies are low. The device physics underlying this proposed hardening technique was studied by measuring light output, total current, and radiative decay time as a function of voltage before and after successive neutron irradiations. Results are presented and discussed. (WHK)
- Research Organization:
- Sandia Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- EY-76-C-04-0789
- OSTI ID:
- 7321156
- Report Number(s):
- SAND-77-0171C; CONF-770714-1; TRN: 77-014668
- Resource Relation:
- Conference: IEEE conference on nuclear and space radiation effects, Williamsburg, VA, USA, 12 Jul 1977
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
LIGHT EMITTING DIODES
RADIATION HARDENING
CARRIER LIFETIME
CRYSTAL DOPING
DIFFUSION LENGTH
ELECTRIC CURRENTS
GALLIUM ARSENIDES
GERMANIUM ADDITIONS
NEUTRONS
PERFORMANCE
PHYSICAL RADIATION EFFECTS
ALLOYS
ARSENIC COMPOUNDS
ARSENIDES
BARYONS
CURRENTS
ELEMENTARY PARTICLES
FERMIONS
GALLIUM COMPOUNDS
GERMANIUM ALLOYS
HADRONS
HARDENING
LIFETIME
NUCLEONS
PNICTIDES
RADIATION EFFECTS
SEMICONDUCTOR DEVICES
SEMICONDUCTOR DIODES
440200* - Radiation Effects on Instrument Components
Instruments
or Electronic Systems