<s>
Geometric	B-Algorithm
diodes	I-Algorithm
,	O
also	O
known	O
as	O
morphological	B-Algorithm
diodes	I-Algorithm
,	O
use	O
the	O
shape	O
of	O
their	O
structure	O
and	O
ballistic	O
/	O
quasi-ballistic	O
electron	O
transport	O
to	O
create	O
diode	O
behavior	O
.	O
</s>
<s>
Geometric	B-Algorithm
diodes	I-Algorithm
differ	O
from	O
all	O
other	O
forms	O
of	O
diodes	O
because	O
they	O
do	O
not	O
rely	O
on	O
a	O
depletion	B-Algorithm
region	I-Algorithm
or	O
a	O
potential	O
barrier	O
to	O
create	O
their	O
diode	O
behavior	O
.	O
</s>
<s>
Instead	O
of	O
a	O
potential	O
barrier	O
,	O
an	O
asymmetry	O
in	O
the	O
geometry	O
of	O
the	O
material	O
(	O
that	O
is	O
on	O
the	O
order	O
of	O
the	O
mean	B-Algorithm
free	I-Algorithm
path	I-Algorithm
of	O
the	O
charge	O
carrier	O
)	O
creates	O
an	O
asymmetry	O
in	O
forward	O
vs	O
reverse	O
bias	O
current	O
(	O
aka	O
a	O
diode	O
)	O
.	O
</s>
<s>
Geometric	B-Algorithm
diodes	I-Algorithm
are	O
formed	O
from	O
one	O
continuous	O
material	O
(	O
adding	O
a	O
caveat	O
for	O
2D-electron	O
gasses	O
which	O
are	O
layered	O
systems	O
)	O
that	O
has	O
an	O
asymmetry	O
in	O
the	O
structure	O
on	O
the	O
order	O
of	O
the	O
size	O
of	O
the	O
charge	O
carrier	O
's	O
mean	B-Algorithm
free	I-Algorithm
path	I-Algorithm
(	O
MFP	O
)	O
.	O
</s>
<s>
This	O
means	O
that	O
to	O
create	O
a	O
geometric	B-Algorithm
diode	I-Algorithm
,	O
one	O
must	O
either	O
use	O
a	O
high	O
MFP	O
material	O
,	O
or	O
have	O
a	O
fabrication	O
process	O
that	O
has	O
nanometer	O
precision	O
in	O
order	O
to	O
create	O
the	O
relevant	O
geometries	O
.	O
</s>
<s>
Geometric	B-Algorithm
diodes	I-Algorithm
are	O
majority	O
carrier	O
devices	O
that	O
do	O
not	O
need	O
a	O
potential	O
barrier	O
.	O
</s>
<s>
Quite	O
simply	O
geometric	B-Algorithm
diodes	I-Algorithm
can	O
be	O
thought	O
of	O
as	O
funnels	O
or	O
lobster	O
traps	O
for	O
charges	O
;	O
In	O
one	O
direction	O
it	O
is	O
relatively	O
easy	O
for	O
charges	O
to	O
flow	O
,	O
and	O
in	O
the	O
reverse	O
direction	O
it	O
is	O
more	O
difficult	O
.	O
</s>
<s>
Geometric	B-Algorithm
diodes	I-Algorithm
could	O
theoretically	O
achieve	O
zero-bias	O
turn-on	O
voltage	O
due	O
to	O
their	O
lack	O
of	O
potential	O
barrier	O
.	O
</s>
<s>
With	O
zero-bias	O
turn-on	O
voltage	O
,	O
there	O
is	O
no	O
DC	O
bias	O
that	O
must	O
be	O
supplied	O
to	O
the	O
device	O
;	O
therefor	O
,	O
geometric	B-Algorithm
diodes	I-Algorithm
could	O
greatly	O
reduce	O
the	O
power	O
needed	O
for	O
to	O
operate	O
a	O
device	O
.	O
</s>
<s>
Geometric	B-Algorithm
diodes	I-Algorithm
lack	O
of	O
potential	O
barrier	O
means	O
they	O
can	O
have	O
ultra-low	O
capacitance	O
down	O
to	O
the	O
attofarads	O
.	O
</s>
<s>
A	O
geometric	B-Algorithm
diode	I-Algorithm
's	O
frequency	O
response	O
is	O
limited	O
not	O
by	O
RC	O
time	O
or	O
minority	O
carrier	O
mobility	O
,	O
but	O
by	O
the	O
flight	O
time	O
of	O
the	O
charge	O
carriers	O
through	O
the	O
structural	O
asymmetry	O
.	O
</s>
<s>
Therefore	O
,	O
geometric	B-Algorithm
diodes	I-Algorithm
can	O
achieve	O
frequency	O
response	O
into	O
the	O
THz	O
.	O
</s>
<s>
The	O
ability	O
for	O
a	O
geometric	B-Algorithm
diode	I-Algorithm
's	O
electronic	O
properties	O
to	O
be	O
tuned	O
by	O
the	O
geometry	O
of	O
the	O
structure	O
,	O
the	O
surface	O
coating	O
on	O
the	O
structure	O
,	O
and	O
the	O
properties	O
of	O
the	O
material	O
used	O
offer	O
a	O
level	O
customization	O
that	O
is	O
unrealized	O
in	O
any	O
other	O
diode	O
system	O
.	O
</s>
<s>
Principles	O
learned	O
from	O
geometric	B-Algorithm
diodes	I-Algorithm
and	O
ballistic	O
systems	O
will	O
be	O
used	O
in	O
understanding	O
technology	O
as	O
devices	O
become	O
increasingly	O
on	O
small	O
and	O
exist	O
at	O
or	O
below	O
charge	O
carrier	O
MFPs	O
.	O
</s>
<s>
The	O
main	O
one	O
being	O
that	O
the	O
reverse	O
bias	O
current	O
from	O
a	O
geometric	B-Algorithm
diode	I-Algorithm
can	O
be	O
quite	O
high	O
(	O
anywhere	O
from	O
three	O
to	O
less	O
than	O
one	O
orders	O
of	O
magnitude	O
less	O
than	O
the	O
forward	O
bias	O
current	O
)	O
.	O
</s>
<s>
Typically	O
geometric	B-Algorithm
diodes	I-Algorithm
are	O
on	O
the	O
nano-scale	O
,	O
so	O
that	O
necessarily	O
means	O
that	O
have	O
high	O
resistances	O
.	O
</s>
<s>
Perhaps	O
the	O
largest	O
hurdle	O
for	O
geometric	B-Algorithm
diodes	I-Algorithm
to	O
overcome	O
is	O
the	O
reliability	O
of	O
their	O
fabrication	O
and	O
ability	O
to	O
scale	O
it	O
up	O
.	O
</s>
<s>
Geometric	B-Algorithm
diodes	I-Algorithm
are	O
typically	O
made	O
using	O
nanofabrication	B-Algorithm
methods	O
that	O
do	O
not	O
scale	O
up	O
well	O
,	O
but	O
with	O
the	O
increasing	O
resolution	O
of	O
photolithography	B-Algorithm
this	O
may	O
not	O
be	O
a	O
problem	O
for	O
long	O
.	O
</s>
<s>
Geometric	B-Algorithm
diodes	I-Algorithm
are	O
linked	O
to	O
the	O
phenomena	O
of	O
electron	O
ratchets	O
,	O
and	O
their	O
histories	O
are	O
intermingled	O
.	O
</s>
<s>
Early	O
work	O
on	O
geometric	B-Algorithm
diodes	I-Algorithm
used	O
2D	O
electron	O
gasses	O
(	O
2DEG	O
)	O
at	O
cryogenic	O
temperatures	O
because	O
these	O
material	O
systems	O
have	O
a	O
very	O
long	O
charge	O
carrier	O
MFP	O
.	O
</s>
<s>
Additionally	O
,	O
a	O
different	O
,	O
two-terminal	O
geometry	O
resembling	O
the	O
simple	O
geometric	B-Algorithm
diode	I-Algorithm
schematic	O
was	O
demonstrated	O
in	O
2013	O
.	O
</s>
<s>
Geometric	B-Algorithm
diodes	I-Algorithm
formed	O
from	O
etched	O
Silicon	O
nanowires	B-Architecture
were	O
shown	O
to	O
operate	O
at	O
room-temperature	O
in	O
April	O
2020	O
.	O
</s>
<s>
This	O
work	O
highlights	O
the	O
tunability	O
of	O
geometric	B-Algorithm
diodes	I-Algorithm
by	O
thoroughly	O
studying	O
the	O
effects	O
of	O
geometry	O
on	O
the	O
diode	O
's	O
electronic	O
properties	O
.	O
</s>
