Group III nitride substrate with oxygen gradient, method of making, and method of use
Embodiments of the present disclosure include techniques related to techniques for processing materials for manufacture of group-III metal nitride and gallium based substrates. More specifically, embodiments of the disclosure include techniques for substrates with a controlled oxygen gradient using a combination of processing techniques. Merely by way of example, the disclosure can be applied to growing crystals of GaN, AlN, InN, InGaN, AlGaN, and AlInGaN, and others for manufacture of bulk or patterned substrates. Such bulk or patterned substrates can be used for a variety of applications including optoelectronic and electronic devices, lasers, light emitting diodes, solar cells, photo electrochemical water splitting and hydrogen generation, photodetectors, integrated circuits, and transistors, and others.
1 . A free-standing nonpolar or semipolar crystal, comprising a group III metal and nitrogen, wherein the free-standing nonpolar or semipolar crystal comprises:
a wurtzite crystal structure;
a first surface having a crystallographic orientation within 30 degrees of {1 0 −1 0}, a maximum dimension greater than 5 millimeters in a first direction, the first direction comprising a projection of [0 0 0 1] on the first surface, and a maximum dimension greater than 15 millimeters in a second direction orthogonal to the first direction;
a second surface on an opposite side of the crystal from the first surface, wherein a separation distance between the first surface and the second surface is between 100 micrometers and 1000 micrometers; and
an average concentration of stacking faults on the first surface below 103 cm −1 ,
wherein the crystal is characterized by an oxygen concentration having a minimum value between 2×10 17 cm −3 and 1×10 19 cm −3 at a first position along the first surface and increasing along points in the first direction to a maximum value between 1×10 18 cm −3 and about 5×10 19 cm −3 at a second position along the first direction, the second position being separated from the first position by a distance between 1 millimeter and 25 millimeters along the first direction.
2 . The free-standing nonpolar or semipolar crystal of claim 1 , wherein the crystal is further characterized by an oxygen concentration having a locally-minimum value between 2×10 17 cm −3 and 1×10 19 cm −3 at a third position along the first surface and having a locally-maximum value between 1×10 18 cm −3 and about 5×10 19 cm −3 at a fourth position along the first direction, the third position being separated from the second position by a distance between 1 millimeter and 25 millimeters and the fourth position being separated from the third position by a distance between 1 millimeter and 25 millimeters along the first direction.
3 . The free-standing nonpolar or semipolar crystal of claim 1 , wherein the crystal is characterized by an oxygen concentration having a minimum value between 5×10 17 cm −3 and 6×10 18 cm −3 at a first position along the first surface and increasing to a locally-maximum value between 2×10 18 cm −3 and 1.2×10 19 cm −3 at a second position along the first direction, the second position being separated from the first position by a distance between 2 millimeters and 10 millimeters along the first direction.
4 . The free-standing nonpolar or semipolar crystal of claim 1 , wherein the crystal is further characterized by an oxygen concentration having a locally-minimum value between 5×10 17 cm −3 and 6×10 18 cm −3 at a third position along the first surface and having a locally-maximum value between 2×10 18 cm −3 and 1.2×10 19 cm −3 at a fourth position along the first direction, the third position being separated from the second position by a distance between 1 millimeter and 25 millimeters and the fourth position being separated from the third position by a distance between 1 millimeter and 25 millimeters along the first direction.
5 . The free-standing nonpolar or semipolar crystal of claim 1 , further comprising an impurity concentration of H greater than 10 17 cm −3 , and an impurity concentration of at least one of Li, Na, K, F, Cl, Br, and I greater than 10 15 cm −3 , as quantified by calibrated secondary ion mass spectrometry.
6 . The free-standing nonpolar or semipolar crystal of claim 1 , wherein the first surface is characterized by average impurity concentrations of:
oxygen (O) between 1×10 16 cm −3 and 5×10 19 cm −3 ;
hydrogen (H) between 1×10 16 cm −3 and 8×10 19 cm −3 ; and
at least one of fluorine (F) and chlorine (Cl) between 1×10 15 cm −3 and 1×10 19 cm −3 .
7 . The free-standing nonpolar or semipolar crystal of claim 1 , wherein an oxygen gradient, defined as a difference between an average oxygen concentration within a depth of 2 to 10 micrometers on the first surface at the first position and the average oxygen concentration within a depth of 2 to 10 micrometers on the first surface at the second position, divided by the separation in the first direction between the first position and the second position, is between about 1×10 21 cm −4 and about 5×10 16 cm −4 .
8 . The free-standing nonpolar or semipolar crystal of claim 7 , wherein the oxygen gradient is between about 5×10 20 cm −4 and about 2×10 17 cm −4 .
9 . The free-standing nonpolar or semipolar crystal of claim 1 , wherein a total thickness variation between the first surface and the second surface is less than about 3 micrometers.
10 . The free-standing nonpolar or semipolar crystal of claim 5 , wherein the first surface is characterized by impurity concentrations of oxygen (O) and hydrogen (H) wherein an average ratio of H and O concentrations is between about 0.3 and about 10.
11 . The free-standing nonpolar or semipolar crystal of claim 6 , wherein the first surface is characterized by impurity concentrations of oxygen (O) and fluorine (F) wherein a ratio of F and O concentrations is between about 0.05% and about 10%.
12 . A free-standing nonpolar or semipolar crystal, comprising a group III metal and nitrogen, wherein the free-standing nonpolar or semipolar crystal comprises:
a wurtzite crystal structure;
a first surface having a crystallographic orientation within 30 degrees of {1 0 −1 0}, a maximum dimension greater than 5 millimeters in a first direction, the first direction comprising a projection of [0 0 0 1] on the first surface, and a maximum dimension greater than 15 millimeters in a second direction orthogonal to the first direction;
a second surface on an opposite side of the crystal from the first surface, wherein a separation distance between the first surface and the second surface is between 100 micrometers and 1000 micrometers; and
an average concentration of stacking faults on the first surface below 10 3 cm −1 ,
wherein the crystal is characterized by an oxygen concentration having a minimum value between 2×10 17 cm −3 and 1×10 19 cm −3 at a first position along the first surface and increasing along all points in the [0 0 0 1] direction to a maximum value between 1×10 18 cm −3 and about 5×10 19 cm −3 at a second position along the first direction, the second position being separated from the first position by a distance between 1 millimeter and 25 millimeters along the first direction.