The change of concentration

depth and capture cross section of deep level for

p

+

-

n

GaAs

1-x

P

x

LED’s during degradation at large current (

J

=250A/cm

2

) for about 750 hours was investigated by DLTS techniques at room temperature

and their luminescence spectra

luminous fluxs and

C-V

and

I-V

characteristics were measured. The parameters of deep level before and after degradation are listed in Table 1.It was observed that there were three electron energy levels [△

E

n1

=0.19±0.01) eV; △

E

n2

=(0.20±0.01)eV; △

E

n3

=(0.40±0.01)eV] in GaAs

1-x

P

x

LED. No new deep level was found after degradation. The luminous efficiency of LED was reduced by 20-35% and then tended to be saturated during aging process

as shown in Fig.3. Experimental results show that the deep energy level density of △

E

n1

△

E

n2

is decreased

while △

E

n3

is increased and its capture cross section is larger. Thereby the △En 1 of capture ration is relatively increased after degradation. As shown in Table 1 the proportion of capture probability of △

E

n3

is increased

although total capture probability of the three energy levels remains almost constant. The capture probability of △

E

n3

is increased by 9

15

26 and 30% respectively and 20% in average for 1

#

-4

#

LED’s. Whereas luminous effoiency is decreased about 21%. The results are agreed very well. This means that the decreace of luminous efficiency after degradation is mainly due to △

E

n3

and △

E

n1

△

E

n2

do not influence the luminous efficiency and degradation characteristic at all. Fig.3 shows that the forward threshold voltage and reverse breakdown voltage of GaAs

1-x

P

x

LED are decreased after degradation. This means that

p-n

junction is damaged and the leakage current is increased with degradation. This may be one of the reasons for the reducing of GaAs

1-x

P

x

LED luminous efficiency.