Browse Prior Art Database

Junction Confined Laser

IP.com Disclosure Number: IPCOM000101924D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Rogers, DL: AUTHOR

Abstract

A new geometry is disclosed for a double heterojunction diode laser which uses a diffused p-n junction to laterally confine the current flow to the active lasing region, thereby lowering the threshold.

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Junction Confined Laser

       A new geometry is disclosed for a double heterojunction
diode laser which uses a diffused p-n junction to laterally confine
the current flow to the active lasing region, thereby lowering the
threshold.

      As shown in Fig. 1, the geometry is similar to other double
heterojunction lasers with a small band gap semiconductor layer 10
sandwiched between two wide band gap semiconductor layers 12, 14 of
opposite polarity, for example, n-type and p-type, respectively.  In
the present structure, an additional diffusion or ion implantation 16
is made which is of the same polarity as the buried layer 14.  This
diffusion creates additional p-n junctions 18 which prevent current
from contact 20 from flowing laterally away from the active region
22.  Why this current flow is inhibited is shown in Fig. 2.

      Fig. 2 shows band diagrams for the junctions labelled A and B
in Fig. 1.  It can be seen that the barrier for current flow in
junction B is always larger than for current flow in junction A.  The
reason for this is that the fermi level on the diffused side of
junction B is forced to be almost equal to the fermi level of the
active region 22 below junction A.  Since the active region is
usually lightly doped and the diffused region of junction B is
heavily doped, the conduction bands in these two regions differ by a
large amount (more than the band gap difference).  Since the
conduction band in region B is much higher, almost a...