GaAs detector

Gallium Arsenide detector

Comparison data of different xray detector with different semiconductor properties. File:Detector comparison ss.pptx

Goal

Testing the viability of an xray detector made using GaAs substrate. This could result in a detector which does not need to be cooled, perhaps just stabilized and this would result in much simpler packaging requirements. Still have to protect the detector from light, which a moderately xray transparent window. We do not require low energy performance for the primary applications where a very low cost analyzer would be targeted.

Log

I am starting with a detector which is 2mm square with a rectangular anode around the periphery of the device. The first two detectors are from batch 3897F2, as noted from the plastic box I received them in. The second batch of detectors are from batch 3902A4.

For reference I've collected V-I curve data for a Si-pin diode taken on a sample from an Amptek detector amptek-si-pin.

Initial detector

This is the device mounted on a pcb, with a closeup of the device.

Mounted on pcb

Closeup mounted

Here is the schematic for the pcb designed to hold this device. File:Schematic-501-12270916.pdf Here is the physical layout. File:Layout-501-12270916.pdf

Detector #1, 3897F2

Data acquired on 5/28/2014 using xl3 as voltage source:

Voltage (no load, V)	Voltage (diode load, V)	Current (measured, uA)
172	88.5	164
145	86	112
125	84	84
95	79	33
85	76	19
76	72	8.6
66	64	4.6
58	56	3.6
46	46	2.6

Detector #2, 3897F2

Data acquired on 5/29/2014 using bench supplies:

Voltage (diode load, V)	Current (measured, uA)
Forward bias
1.0	0.0
2.0	0.0
3.0	0.0
5.0	0.1
10	0.3
15	0.5
20	0.7
30	1.3
40	2.0
50	2.6
60	3.3
Reverse bias
10.1	0.4
20.1	1.0
30	1.7
40	2.5
50	3.6
60	5.0
70	9.7
80	71
85	141
86	152
87	170
88	190
89	210

Detector #3, 3902A4

Data acquired on 6/9/2014 using bench supplies:

Reverse bias
Voltage (diode load, V)	Current (measured, uA)
10	0.9
20	1.9
30	2.9
40	4.5
50	6.3
60	8.9
65	11
70	15.9
75	33.2
78	59
80	81.5
81	95
82	112
83	131
84	152
85	178

Forward bias
Voltage (diode load, V)	Current (measured, uA)
10	1.1
20	2.2
30	3.3
40	4.5
50	6.0
60	8.5
65	11.0
70	18.5
75	37
78	54
80	69.5
81	77
82	86.7
83	95
84	104
85	114

Detector #4, 3902A4

Data acquired on 6/9/2014 using bench supplies:

Reverse bias
Voltage (diode load, V)	Current (measured, uA)
10	1.0
20	2.0
30	3.4
40	5.2
50	7.4
60	17
65	40
70	88
75	90
78	75
80	89
81	101
82	112
83	127
84	135
85	141

Measurements from 60V to 85V all suffered from large current swings (> 5uA). The current draw appeared somewhat unstable, so there is substantial error in the current measurements.

Forward bias
Voltage (diode load, V)	Current (measured, uA)
10	1.0
20	2.3
30	3.4
40	5.1
50	7.0
60	10.1
65	12.6
70	17.8
75	26.8
78	34.8
80	42.4
81	46.3
82	50.9
83	61.0
84	65.5
85	71.0

Detector #5, 3944A1

Data acquired on 6/19/2014 using bench supplies:

Reverse bias
Voltage (diode load, V)	Current (measured, uA)
10	0.3
20	0.8
30	1.4
40	2.2
50	3.5
60	5.4
70	8.7
80	21.7
90	65
92	77
94	94
96	120
98	150
100	193

Forward bias
Voltage (diode load, V)	Current (measured, uA)
10	0.5
20	1.2
30	1.8
40	2.4
50	3.0
60	3.9
70	5.8
80	13.7
90	25.1
100	36.7
110	47.3
120	56.8
130	65.7
140	62.2
150	62.8
160	63.3
170	62.8
180	62.8
190	62.8
200	62.7

Detector #6, 3944A1

Data acquired on 6/19/2014 using bench supplies:

Reverse bias
Voltage (diode load, V)	Current (measured, uA)
10	0.3
20	0.9
30	1.6
40	2.7
50	4.3
60	8.1
70	20.6
80	63.9
85	105
90	184
92	215

Forward bias
Voltage (diode load, V)	Current (measured, uA)
10	0.4
20	1.0
30	1.5
40	2.0
50	2.5
60	3.2
70	4.4
80	9.6
90	40.0
100	132
101	130
102	146
103	161
104	176
105	203

Detector #7, 3953C3

Measured capacitance with LCR Meter BK Precision 879, 39pF.

Data acquired on 8/14/2014 using bench supplies:

Image of the device #7 and #8.

thin intrinsic layer detector

These two detectors have intrinsic layers that are 10um thick. The n-side is 150um thick and the p-side is 1um thick? The "active area" is the center anode contact and there is a guard ring as can be seen in the picture. At this point I have utilized the guard ring.

Observed odd behavior. When measuring the reverse bias I noticed that when I gradually ramp the voltage up to 70V (for example) the measured current draw stays low, as described in the table. However, if I apply the voltage instantly at 70V and look at the current draw it starts high and goes down "slowly" over time to approximately the steady state values below. There appears to be non-trivial capacitance incorporated in to the device.

Reverse bias (dark, covered)
Voltage (applied, V)	Current (measured, uA) (10k ohm resistor in series)
10	0.0
20	0.1
30	0.1
40	0.1
50	0.1
60	0.11
70	0.15
72	0.13
74	0.15
76	0.17
80	0.2
85	0.2
90	0.1
95	0.1
100	0.1
105	0.1
110	142
115	188.9
Forward bias (dark, covered)
Voltage (applied, V)	Current (measured, uA) (10k ohm resistor in series)
0	0.06
0.1	0.06
0.2	0.08
0.4	0.08
0.5	0.09
0.6	0.23
0.7	1.38
0.8	2.77
0.9	9.17
1.0	17.6
1.1	27.2
1.2	32.3
1.3	42.6
1.4	49.7
1.5	60.6
1.6	71.0
1.7	80.3
1.83	91.4
1.95	102
2.11	118
2.24	130
2.37	143

Detector #8, 3953C4

Measured capacitance with LCR Meter BK Precision 879, 281pF.

Data acquired on 8/14/2014 using bench supplies:

Reverse bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
10	0.08
20	0.09
30	0.08
40	0.08
50	0.09
60	0.09
70	0.10
80	0.10
90	0.42
100	1.64
105	2.72
108	3.61
109	40.4
110	95.5
forward bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.09
0.13	0.09
0.25	0.08
0.43	0.11
0.48	0.2
0.54	0.56
0.65	2.92
0.78	9.32
0.89	17.4
1.01	26.5
1.19	41.2
1.32	52.4
1.43	62.6
1.65	82.9
1.94	110

Detector #9, 3956B1

Measured capacitance with LCR Meter BK Precision 879, 50pF.

Data acquired on 8/19/2014 using bench supplies:

New devices which should have lower P contamination.

Reverse bias (dark, covered)
Voltage (applied, V)	Current (measured, uA) (10k ohm resistor in series)
10	0.8
20	0.12
30	0.33
40	0.59
50	0.93
60	1.29
70	1.82
72	1.98
74	2.16
76	2.34
80	3.01
85	4.85
90	240
95	280
100	306
105	325
110	350
115	372
Forward bias (dark, covered)
Voltage (applied, V)	Current (measured, uA) (10k ohm resistor in series)
0	0.09
0.13	0.08
0.247	0.08
0.364	0.08
0.423	0.14
0.601	4.71
0.718	13.21
0.834	22.9
0.886	27.5
1.0	38.5
1.125	49.41
1.24	60.3
1.3	65.8
1.384	73.7
1.475	82.3
1.53	87.8
1.65	98.9
1.82	115
1.94	127
2.05	138
2.29	161
2.52	183

Detector #10, 3956F3

Measured capacitance with LCR Meter BK Precision 879, 50pF.

Data acquired on 8/19/2014 using bench supplies:

Reverse bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
10	0.1
20	0.09
30	0.09
40	0.08
50	0.09
60	0.09
70	0.08
80	0.09
90	0.09
100	0.08
110	0.08
120	0.09
130	0.08
135	0.08
140	62
150	146
160	175
170	395
forward bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.08
0.13	0.08
0.246	0.08
0.305	0.09
0.423	0.1
0.541	0.14
0.601	0.29
0.719	1.79
0.835	6.76
0.951	14.6
1.07	23.9
1.24	39.2
1.44	56.7
1.54	66.1
1.71	82.3

Detector #11, 3957A2

UPDATE: just learned that this is not a device, just a test article, p-doped only (9/5/2014)

Measured capacitance with LCR Meter BK Precision 879, 57pF.

Data acquired on 9/4/2014 using bench supplies:

Reverse bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.09
10	2.81
20	33.78
30	97.5
40	211
50	410
60
70
80
90
100
110
120
130
135
140
150
160
170
forward bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.08
0.129	0.08
0.188	0.08
0.246	0.08
0.363	0.08
0.481	0.10
0.549	0.13
0.661	0.20
0.718	0.25
0.776	0.29
0.893	0.32
0.952	0.33
1.07	0.37
1.19	0.46
1.31	0.68
1.48	3.92
1.66	10.3
1.84	61.0
1.93	84.5
2.07	103.9
2.19	118

Detector #12, 3957A2

UPDATE: just learned that this is not a device, just a test article, p-doped only (9/5/2014)

Measured capacitance with LCR Meter BK Precision 879, 58pF.

Data acquired on 9/4/2014 using bench supplies:

Reverse bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.09
10	2.84
20	23.03
30	64.2
40	138
50	285
60	660
70
80
90
100
110
120
130
135
140
150
160
170
forward bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.08
0.129	0.08
0.199	0.08
0.305	0.08
0.422	0.1
0.481	0.13
0.601	0.29
0.719	0.50
0.777	0.63
0.835	0.77
0.980	1.10
1.11	1.47
1.25	1.92
1.51	3.65
1.66	7.98
1.74	12.81
2.04	32.9
2.30	55.4
2.42	66
2.60	81.5

Detector #13, 3960B2

Measured capacitance with LCR Meter BK Precision 879, 32pF.

Data acquired on 9/9/2014 using bench supplies:

Reverse bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.08
10	0.08
20	0.08
30	0.08
40	0.08
50	0.08
60	0.08
70	0.08
80	0.08
90	0.08
100	0.08
110	0.08
120	0.08
130	0.08
135	0.08
140	0.08
150	0.08
160	0.08
170	0.08
forward bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.08
0.137	0.08
0.245	0.08
0.362	0.08
0.480	0.14
0.539	0.26
0.599	0.59
0.658	1.39
0.762	4.82
0.892	12.2
0.951	16.24
1.01	20.6
1.19	34.9
1.37	50.6
1.42	55.4
1.54	65.8
1.60	71.3
1.84	93.1
1.95	104
2.13	120

Detector #14, 3962A1

Measured capacitance with LCR Meter BK Precision 879, 22pF. This is a BAE wafer 73um thick. There were issues with wafer reported to me.

Data acquired on 9/25/2014 using bench supplies:

Reverse bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.08
10	0.14
20	6.35
30	25.4
40	125
50	700
forward bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.08
0.137	0.08
0.245	0.08
0.362	0.08
0.478	0.10
0.597	0.37
0.715	1.41
0.773	3.03
0.840	6.50
0.890	9.18
1.05	21.1
1.18	32.7
1.24	37.9
1.42	53.9
1.48	59.4
1.59	70.3
1.77	86.9
1.95	103
2.06	115

Detector #15, 3963A1

Measured capacitance with LCR Meter BK Precision 879, 45pF. BAE wafer 40um thick. Reported issues with wafer quality.

Data acquired on 9/25/2014 using bench supplies:

Reverse bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.08
10	3.25
20	26.9
30	142
40	320
50	546
forward bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.08
0.137	0.08
0.245	0.08
0.362	0.08
0.480	0.14
0.539	0.26
0.599	0.59
0.658	1.39
0.762	4.82
0.892	12.2
0.951	16.24
1.01	20.6
1.19	34.9
1.37	50.6
1.42	55.4
1.54	65.8
1.60	71.3
1.84	93.1
1.95	104
2.13	120

Detector #16, 3960B2

Measured capacitance with LCR Meter BK Precision 879, 75pF. 20um thick, 2mm square.

Data acquired on 9/26/2014 using bench supplies:

Reverse bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.08
10	0.08
80	0.08
90	0.10
130	0.11
170	0.12
190	0.13
230	0.40
240	0.50
250	0.60
260	0.80
270	0.83
280	0.86
290	0.87
300	1.58
forward bias (dark, covered)
Voltage (diode load, V) (10k ohm in series)	Current (measured, uA)
0	0.08
0.192	0.08
0.310	0.08
0.368	0.08
0.420	0.10
0.486	0.26
0.603	1.65
0.663	3.58
0.780	9.93
0.897	18.4
1.07	32.9
1.13	38.0
1.19	34.9
1.19	43.2
1.25	48.4
1.31	54.1
1.39	61.2
1.48	69.8
1.60	80.7
1.78	97.2

Reverse bias data acquired on 10/15/2014 using bench supply, measuring current by measuring voltage drop across 1M ohm resistor:

Reverse bias (dark, covered)
Voltage (diode load, V)	Current (calculated uA, 1M ohm voltage drop)	Min max values after ~60 secs dwell
V	min uA	max uA
0	-0.014	-0.015
10	0.997	0.998
20	1.999	1.993
30	3.004	3.006
40.12	3.996	3.998
50.02	4.994	4.995
59.95	6.037	6.045
70.0	7.059	7.062
80.06	8.078	8.080
90.01	9.089	9.097
99.95	10.103	10.106
110.0	11.132	11.140
120.02	12.166	12.170
130	13.209	13.231
140.03	14.279	14.327
150.08	15.466	15.568
160.12	17.001	17.315
170.2	19.386	20.614
180.5	24.331	25.738
190.1	31.721	32.459
200.2	43.243	44.271