23.4 Lasers
665
Fig. 23.36 Laser with a
homojunction, b single
heterostructure (SHS), c
double heterostructure
(‘DHS’), d reduction of
threshold current with
design progress (‘SHS’:
d =2 µm, ‘DHS’:
d =0.5 µm). Adapted
from [1982]
E
n
n
GaAs
p
GaAs
n
GaAs
n
GaAs
p
AlGaAs
p
AlGaAs
n
AlGaAs
p
GaAs
(d)
100
150
200
250
300
T
j (A/cm )
2
10
5
10
10
10
4
3
2
homo
DHS
SHS
GaAs/AlGaAs
Fig. 23.37 Schematic
band diagram of a pn
double heterostructure
(DHS) diode
(InP/InGaAsP/InP) a
before contact of the
materials, b in
thermodynamic
equilibrium (zero bias,
dashed line is Fermi level
E F = const.), c with
forward bias close to
flat-band conditions,
dashed lines are
quasi-Fermi levels. χ core
denotes the electron affinity
of the core material, χ cl
that of the cladding layers
665
Fig. 23.36 Laser with a
homojunction, b single
heterostructure (SHS), c
double heterostructure
(‘DHS’), d reduction of
threshold current with
design progress (‘SHS’:
d =2 µm, ‘DHS’:
d =0.5 µm). Adapted
from [1982]
E
n
n
GaAs
p
GaAs
n
GaAs
n
GaAs
p
AlGaAs
p
AlGaAs
n
AlGaAs
p
GaAs
(d)
100
150
200
250
300
T
j (A/cm )
2
10
5
10
10
10
4
3
2
homo
DHS
SHS
GaAs/AlGaAs
Fig. 23.37 Schematic
band diagram of a pn
double heterostructure
(DHS) diode
(InP/InGaAsP/InP) a
before contact of the
materials, b in
thermodynamic
equilibrium (zero bias,
dashed line is Fermi level
E F = const.), c with
forward bias close to
flat-band conditions,
dashed lines are
quasi-Fermi levels. χ core
denotes the electron affinity
of the core material, χ cl
that of the cladding layers